All questions of Friction for Grade 9 Exam
The shape of an aeroplane is like a- a)Bird
- b)Car
- c)Dog
- d)All.
Correct answer is option 'A'. Can you explain this answer?
The shape of an aeroplane is like a
a)
Bird
b)
Car
c)
Dog
d)
All.
|
Vivek Rana answered |
Airplanes have wings, just like birds. They also have a light Skelton to decrease their weight, and they have a streamlined shape to decrease drag. Airplanes wings are designed to create lift by changing the pressure, rather than by flapping them up and down.
Fluids are only liquids.- a)True
- b)False
Correct answer is option 'B'. Can you explain this answer?
Fluids are only liquids.
a)
True
b)
False
|
Kavya Saxena answered |
A fluid is a substance that continually flows under an applied shear stress, or external force. Fluids are a phase of matter and include liquids, gases and plasmas.
Sliding friction is ______________ than static friction.- a)More
- b)Equal
- c)Greater
- d)Less
Correct answer is option 'D'. Can you explain this answer?
Sliding friction is ______________ than static friction.
a)
More
b)
Equal
c)
Greater
d)
Less
|
Amit Sharma answered |
- Friction comes into play when irregularities present in the surfaces of two objects in contact get interlocked with each other.
- In sliding, the time given for interlocking is very small. Hence, the interlocking is not strong.
- Therefore, less force is required to overcome this interlocking. Because of this reason, sliding friction is less than static friction.
Rolling friction is smaller than- a)Sliding friction
- b)Static friction
- c)Fluid friction
- d)All of the above.
Correct answer is option 'D'. Can you explain this answer?
Rolling friction is smaller than
a)
Sliding friction
b)
Static friction
c)
Fluid friction
d)
All of the above.
|
Malavika Basu answered |
No the correct answer is
(a) Sliding friction
Explanation: Friction is the force which resists the relative motion between two surfaces in contact.
Now, rolling friction comes into play between two surfaces, when one body rolls over the other and sliding friction comes into play when when one body slides or tends to slide over the surface of another body; it tends to reduce the relative velocity between the two surfaces during sliding. Now, if the area of contact between the two surfaces can somehow be reduced, then the effect of friction between the two surfaces will be drastically reduced.
When an object slides across the ground, it has much more surface area in direct contact with the ground, which means that the amount of friction is significantly higher. When an object rolls along the ground, only a minuscule point on the object contacts the ground at any point in time, making the stopping force much weaker.
Moreover, in sliding motion, the heights of cavities (irregularities) are to climb up which introduces the friction, while rolling friction, the heights of cavitites are to cross over which avoid the friction.
A toy car released with the same initial speed will travel farthest on- a)Muddy surface
- b)Cemented surface
- c)Brick surface
- d)Polished marble surface
Correct answer is option 'D'. Can you explain this answer?
A toy car released with the same initial speed will travel farthest on
a)
Muddy surface
b)
Cemented surface
c)
Brick surface
d)
Polished marble surface
|
|
Kavya Saxena answered |
A polished marble surface has the least frictional force, hence a car will travel farther on a marble floor.
Fluid friction can be minimized by:
- a)Adding salts to fluid
- b)Increasing volume
- c)Giving suitable shape
- d)Decreasing volume
Correct answer is option 'C'. Can you explain this answer?
Fluid friction can be minimized by:
a)
Adding salts to fluid
b)
Increasing volume
c)
Giving suitable shape
d)
Decreasing volume
|
Aniket Choudhary answered |
Fluid friction can be minimized by giving suitable shapes to the objects moving in the fluids.
Smooth surface has less frictional force.- a)True
- b)False
Correct answer is option 'A'. Can you explain this answer?
Smooth surface has less frictional force.
a)
True
b)
False
|
Rajat Malik answered |
Explanation:
Introduction:
Frictional force is a force that opposes the motion of an object when it is in contact with a surface. It acts parallel to the surface and depends on the nature of the surfaces in contact and the force pressing them together.
Smooth Surface:
A smooth surface is one that is even, polished, and free from roughness or unevenness. It has a low coefficient of friction, which means that there is less resistance to motion when an object moves across it.
Frictional Force:
Frictional force is the force that opposes the motion of an object. It arises due to the interaction between the surfaces in contact. The magnitude of the frictional force depends on two factors: the nature of the surfaces in contact and the force pressing them together.
Less Frictional Force:
When the surface is smooth, there are fewer irregularities or roughness on the surface, which reduces the points of contact between the two surfaces. This results in a smaller surface area in contact, reducing the frictional force. Additionally, the smooth surface allows objects to slide or move more easily, further reducing the frictional force.
Explanation:
The statement "Smooth surface has less frictional force" is true. A smooth surface has less frictional force compared to a rough surface. This is because the smooth surface has fewer irregularities or roughness, which reduces the points of contact and the surface area in contact between the two surfaces. As a result, there is less resistance to motion, and the frictional force is reduced.
When objects slide or move on a smooth surface, there is less frictional force acting against the motion. This allows objects to move more easily and smoothly. For example, if you try to slide a heavy object on a rough surface, it would require more force compared to sliding the same object on a smooth surface.
In everyday life, we can observe this phenomenon when we use lubricants like oil or grease on surfaces to reduce friction. The lubricants fill in the gaps and irregularities on the surface, making it smoother and reducing the frictional force.
In conclusion, a smooth surface has less frictional force due to its reduced points of contact and surface area in contact. This allows objects to move more easily and smoothly on a smooth surface compared to a rough surface.
Introduction:
Frictional force is a force that opposes the motion of an object when it is in contact with a surface. It acts parallel to the surface and depends on the nature of the surfaces in contact and the force pressing them together.
Smooth Surface:
A smooth surface is one that is even, polished, and free from roughness or unevenness. It has a low coefficient of friction, which means that there is less resistance to motion when an object moves across it.
Frictional Force:
Frictional force is the force that opposes the motion of an object. It arises due to the interaction between the surfaces in contact. The magnitude of the frictional force depends on two factors: the nature of the surfaces in contact and the force pressing them together.
Less Frictional Force:
When the surface is smooth, there are fewer irregularities or roughness on the surface, which reduces the points of contact between the two surfaces. This results in a smaller surface area in contact, reducing the frictional force. Additionally, the smooth surface allows objects to slide or move more easily, further reducing the frictional force.
Explanation:
The statement "Smooth surface has less frictional force" is true. A smooth surface has less frictional force compared to a rough surface. This is because the smooth surface has fewer irregularities or roughness, which reduces the points of contact and the surface area in contact between the two surfaces. As a result, there is less resistance to motion, and the frictional force is reduced.
When objects slide or move on a smooth surface, there is less frictional force acting against the motion. This allows objects to move more easily and smoothly. For example, if you try to slide a heavy object on a rough surface, it would require more force compared to sliding the same object on a smooth surface.
In everyday life, we can observe this phenomenon when we use lubricants like oil or grease on surfaces to reduce friction. The lubricants fill in the gaps and irregularities on the surface, making it smoother and reducing the frictional force.
In conclusion, a smooth surface has less frictional force due to its reduced points of contact and surface area in contact. This allows objects to move more easily and smoothly on a smooth surface compared to a rough surface.
Force of friction depends on- a)Smoothness of surface
- b)Roughness of surface
- c)Inclination of surface
- d)All of above.
Correct answer is option 'D'. Can you explain this answer?
Force of friction depends on
a)
Smoothness of surface
b)
Roughness of surface
c)
Inclination of surface
d)
All of above.
|
Sanjana Bose answered |
Friction is the name given to the force that opposes the motion of one body sliding over another. It is called friction when the objects are solid, viscosity in liquids but it always opposes the motion of an object.
The first mathematical description was made by Charles Augustine de Coloumb in 1764. He proposed that friction could be classed as static or dynamic and proposed that the frictional force was frictional force dependent on the materials in contact.
Surface Contact
At an interface between two objects, the surfaces may appear to be smooth, however on a microscopic scale the surfaces are pitted and jagged.
The friction force depends on two factors:
a) The materials that are in contact. The two materials and the nature of their surfaces. Rougher surfaces have higher coefficient of frictions but to slide apart. This makes sense in terms of a model in which friction is described as arising from chemical bonds between the atoms of the two surfaces at their points of contact: very flat surfaces allow more atoms to come in contact
b) The force pushing the two surfaces together. Pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other.
Soapy floor is slippery due to increased friction.- a)True
- b)False
Correct answer is option 'B'. Can you explain this answer?
Soapy floor is slippery due to increased friction.
a)
True
b)
False
|
Geetika Shah answered |
Soapy floor is slippery due to decreased friction. The soap covers the roughness of floor and makes it smooth, which restricts our walk on the floor.
So, the given statement is false.
So, the given statement is false.
In machine, friction between moving part is reduced by- a)Heating machine
- b)Using powder
- c)Using lubricants
- d)Using paints
Correct answer is option 'C'. Can you explain this answer?
In machine, friction between moving part is reduced by
a)
Heating machine
b)
Using powder
c)
Using lubricants
d)
Using paints
|
|
Ananya Das answered |
In machine, friction between moving parts is reduced by using lubricants. These lubricants stick with machine parts to make them smoother that leads to reduction in friction.
Friction is a- a)contact force
- b)non-contact force
- c)magnetic force
- d)none of these.
Correct answer is option 'A'. Can you explain this answer?
Friction is a
a)
contact force
b)
non-contact force
c)
magnetic force
d)
none of these.
|
|
Rahul Negi answered |
The force which always opposes the motion of one body over another body frictional force. It acts between the two surfaces which are in contact with each other. Since frictional force arises when the surface of two objects are in touch with each other ,therefore, frictional force is an example of contact force.
Sprinkling of powder on the carrom board- a)Reduce friction
- b)Make the board durable
- c)Increase friction
- d)Maintain the friction
Correct answer is option 'A'. Can you explain this answer?
Sprinkling of powder on the carrom board
a)
Reduce friction
b)
Make the board durable
c)
Increase friction
d)
Maintain the friction
|
Siddharth Mukherjee answered |
Sliding friction is less than static friction. It is easier to move a heavy object by sliding in comparison to rotating on surface.
The frictional force exerted by fluids is also called- a)Drag
- b)Rung
- c)Smug
- d)Slag
Correct answer is option 'A'. Can you explain this answer?
The frictional force exerted by fluids is also called
a)
Drag
b)
Rung
c)
Smug
d)
Slag
|
Shraddha Menon answered |
The frictional force exerted by fluids is also called as drag. This kinds of frictional force can be reduced by changing the shape of the moving body.
Spring balance is a device used for measuring the force.- a)True
- b)False
Correct answer is option 'A'. Can you explain this answer?
Spring balance is a device used for measuring the force.
a)
True
b)
False
|
Manisha Shah answered |
Explanation:
A spring balance is a device that is used to measure the force exerted on an object. It consists of a spring fixed at one end and a hook at the other end. When a force is applied to the hook, the spring stretches and the amount of stretch is measured using a calibrated scale attached to the spring. The scale is usually marked in units of weight, such as pounds or kilograms.
How does it work?
The spring balance works on the principle of Hooke's Law, which states that the extension of a spring is proportional to the force applied to it. When a force is applied to the hook of the spring balance, the spring stretches and the amount of stretch is proportional to the force applied. This stretch is measured using a calibrated scale attached to the spring.
Uses of spring balance:
Spring balances are used in a variety of applications, including:
- Measuring the weight of an object
- Measuring the force required to compress or stretch a spring
- Measuring the force required to move an object
- Measuring the force required to pull or push an object
- Measuring the force required to lift an object
Advantages of spring balance:
- It is easy to use and does not require any complex setup or calibration
- It is relatively inexpensive compared to other types of force measuring devices
- It is portable and can be used in the field or in remote locations
- It is a non-destructive testing method and does not damage the object being tested
Conclusion:
Therefore, it can be concluded that the given statement "Spring balance is a device used for measuring the force" is true.
A spring balance is a device that is used to measure the force exerted on an object. It consists of a spring fixed at one end and a hook at the other end. When a force is applied to the hook, the spring stretches and the amount of stretch is measured using a calibrated scale attached to the spring. The scale is usually marked in units of weight, such as pounds or kilograms.
How does it work?
The spring balance works on the principle of Hooke's Law, which states that the extension of a spring is proportional to the force applied to it. When a force is applied to the hook of the spring balance, the spring stretches and the amount of stretch is proportional to the force applied. This stretch is measured using a calibrated scale attached to the spring.
Uses of spring balance:
Spring balances are used in a variety of applications, including:
- Measuring the weight of an object
- Measuring the force required to compress or stretch a spring
- Measuring the force required to move an object
- Measuring the force required to pull or push an object
- Measuring the force required to lift an object
Advantages of spring balance:
- It is easy to use and does not require any complex setup or calibration
- It is relatively inexpensive compared to other types of force measuring devices
- It is portable and can be used in the field or in remote locations
- It is a non-destructive testing method and does not damage the object being tested
Conclusion:
Therefore, it can be concluded that the given statement "Spring balance is a device used for measuring the force" is true.
Fluids are only liquids.- a)True
- b)False
Correct answer is option 'B'. Can you explain this answer?
Fluids are only liquids.
a)
True
b)
False
|
|
Shubham Sharma answered |
A fluid is a substance that continually flows under an applied shear stress, or external force. Fluids are a phase of matter and include liquids, gases, and plasmas.
So, the given statement is false.
So, the given statement is false.
Friction opposes the __________ between two surfaces in contact.- a)Reflective motion
- b)Relative motion
- c)Rotary motion
- d)Refractive motion
Correct answer is option 'B'. Can you explain this answer?
Friction opposes the __________ between two surfaces in contact.
a)
Reflective motion
b)
Relative motion
c)
Rotary motion
d)
Refractive motion
|
Tejas Iyer answered |
Friction opposes the relative motion between two surfaces in contact. Frictional force acts in opposite direction of motion to slow down the speed of moving body.
Irregularities between two surfaces interlock to produce friction.- a)True
- b)False
Correct answer is option 'A'. Can you explain this answer?
Irregularities between two surfaces interlock to produce friction.
a)
True
b)
False
|
Dipanjan Chaudhary answered |
Irregularities between two surfaces interlock to produce friction.
Explanation:
Friction is the force that opposes the relative motion or tendency of motion between two surfaces in contact. It is a result of the interlocking of irregularities between the surfaces. The irregularities or roughness on the surfaces create resistance, leading to the generation of frictional force. This statement is true and can be explained as follows:
1. Interlocking of irregularities:
When two surfaces come in contact, they may appear smooth at a macroscopic level, but at a microscopic level, they have irregularities or roughness. These irregularities can be in the form of bumps, ridges, or valleys on the surface. When the two surfaces are pressed together, these irregularities interlock with each other.
2. Contact points and friction:
The interlocking of irregularities creates contact points between the surfaces. These contact points are the areas where the surfaces are in direct contact with each other. Friction occurs at these contact points due to the resistance caused by the interlocking irregularities.
3. Resistance and frictional force:
As one surface attempts to slide or move relative to the other, the interlocking irregularities resist this motion. The irregularities act like tiny obstacles that need to be overcome. This resistance results in the generation of frictional force. The greater the irregularities and interlocking, the higher the frictional force.
4. Importance of friction:
Friction is an essential force in our daily lives. It allows us to walk, drive vehicles, grip objects, and perform various tasks. Without friction, objects would slide or slip uncontrollably. The interlocking of irregularities between surfaces provides the necessary grip and stability.
Therefore, the statement "Irregularities between two surfaces interlock to produce friction" is true. The interlocking of irregularities creates contact points and resistance, leading to the generation of frictional force.
Explanation:
Friction is the force that opposes the relative motion or tendency of motion between two surfaces in contact. It is a result of the interlocking of irregularities between the surfaces. The irregularities or roughness on the surfaces create resistance, leading to the generation of frictional force. This statement is true and can be explained as follows:
1. Interlocking of irregularities:
When two surfaces come in contact, they may appear smooth at a macroscopic level, but at a microscopic level, they have irregularities or roughness. These irregularities can be in the form of bumps, ridges, or valleys on the surface. When the two surfaces are pressed together, these irregularities interlock with each other.
2. Contact points and friction:
The interlocking of irregularities creates contact points between the surfaces. These contact points are the areas where the surfaces are in direct contact with each other. Friction occurs at these contact points due to the resistance caused by the interlocking irregularities.
3. Resistance and frictional force:
As one surface attempts to slide or move relative to the other, the interlocking irregularities resist this motion. The irregularities act like tiny obstacles that need to be overcome. This resistance results in the generation of frictional force. The greater the irregularities and interlocking, the higher the frictional force.
4. Importance of friction:
Friction is an essential force in our daily lives. It allows us to walk, drive vehicles, grip objects, and perform various tasks. Without friction, objects would slide or slip uncontrollably. The interlocking of irregularities between surfaces provides the necessary grip and stability.
Therefore, the statement "Irregularities between two surfaces interlock to produce friction" is true. The interlocking of irregularities creates contact points and resistance, leading to the generation of frictional force.
Fluids are- a)gases
- b)liquids
- c)gases and liquids both
- d)none of these.
Correct answer is option 'C'. Can you explain this answer?
Fluids are
a)
gases
b)
liquids
c)
gases and liquids both
d)
none of these.
|
|
Gargi Nambiar answered |
Introduction:
Fluids are substances that can flow and take the shape of the container they are placed in. They are a state of matter and can exist as gases and liquids. In this question, we need to determine which of the given options correctly identify fluids. The correct answer is option C, which states that fluids are both gases and liquids.
Explanation:
1. Gases:
Gases are one of the states of matter and can be considered as fluids. They have particles that are in constant motion and are not held together by strong intermolecular forces. Gases can be compressed and they fill the entire volume of the container they are placed in. Examples of gases include oxygen, nitrogen, carbon dioxide, and helium.
2. Liquids:
Liquids are also a state of matter and are considered fluids. Unlike gases, liquids have particles that are closer together and are held together by intermolecular forces. Liquids have a definite volume but do not have a definite shape. They take the shape of the container they are placed in. Examples of liquids include water, milk, oil, and juice.
3. Fluids are Gases and Liquids:
Fluids encompass both gases and liquids. They share the common property of being able to flow and take the shape of their containers. While gases and liquids have differences in their particle arrangement and intermolecular forces, they both exhibit fluidity. The ability to flow is what defines fluids.
Conclusion:
In conclusion, fluids include both gases and liquids. Gases are characterized by particles that are far apart and can be compressed, while liquids have particles that are closer together and have a definite volume. Both gases and liquids exhibit fluidity, which is the ability to flow and take the shape of the container they are placed in.
Fluids are substances that can flow and take the shape of the container they are placed in. They are a state of matter and can exist as gases and liquids. In this question, we need to determine which of the given options correctly identify fluids. The correct answer is option C, which states that fluids are both gases and liquids.
Explanation:
1. Gases:
Gases are one of the states of matter and can be considered as fluids. They have particles that are in constant motion and are not held together by strong intermolecular forces. Gases can be compressed and they fill the entire volume of the container they are placed in. Examples of gases include oxygen, nitrogen, carbon dioxide, and helium.
2. Liquids:
Liquids are also a state of matter and are considered fluids. Unlike gases, liquids have particles that are closer together and are held together by intermolecular forces. Liquids have a definite volume but do not have a definite shape. They take the shape of the container they are placed in. Examples of liquids include water, milk, oil, and juice.
3. Fluids are Gases and Liquids:
Fluids encompass both gases and liquids. They share the common property of being able to flow and take the shape of their containers. While gases and liquids have differences in their particle arrangement and intermolecular forces, they both exhibit fluidity. The ability to flow is what defines fluids.
Conclusion:
In conclusion, fluids include both gases and liquids. Gases are characterized by particles that are far apart and can be compressed, while liquids have particles that are closer together and have a definite volume. Both gases and liquids exhibit fluidity, which is the ability to flow and take the shape of the container they are placed in.
Friction is a necessary evil.- a)True
- b)False
Correct answer is option 'A'. Can you explain this answer?
Friction is a necessary evil.
a)
True
b)
False
|
M Gj answered |
Friction is a necessary evil because there are many uses of friction in our lives but also there are some disadvantages like wearing out of tires.
So the answer is true.
The substance which reduce friction are called- a)Lubricants
- b)Wheels
- c)Powder
- d)Graphite
Correct answer is option 'A'. Can you explain this answer?
The substance which reduce friction are called
a)
Lubricants
b)
Wheels
c)
Powder
d)
Graphite
|
|
Ananya Das answered |
The substances which reduce friction are called lubricants. Lubricants include graphite, oils and greases. Lubricant stick with moving part to reduce friction.
Substances are called lubricants which are used to- a)increase friction
- b)decrease friction
- c)increase or decrease friction
- d)none of these.
Correct answer is option 'B'. Can you explain this answer?
Substances are called lubricants which are used to
a)
increase friction
b)
decrease friction
c)
increase or decrease friction
d)
none of these.
|
|
Ananya Das answered |
A lubricant is a substance, usually organic, introduced to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces.
What do ball bearings replace in most machines to reduce friction?
- a)Sliding friction
- b)Static friction
- c)Fluid friction
- d)Rolling friction
Correct answer is option 'A'. Can you explain this answer?
What do ball bearings replace in most machines to reduce friction?
a)
Sliding friction
b)
Static friction
c)
Fluid friction
d)
Rolling friction
|
Valor Academy answered |
Ball bearings replace sliding friction with rolling friction in most machines, which significantly reduces resistance and wear.
What happens to the contact points on a surface when an object starts sliding?- a)They interlock more
- b)They do not get enough time to interlock
- c)They become magnetic
- d)They disappear
Correct answer is option 'B'. Can you explain this answer?
a)
They interlock more
b)
They do not get enough time to interlock
c)
They become magnetic
d)
They disappear
|
L Rvi answered |
Friction
is caused by the interlocking of irregularities in the two surfaces. When the object starts sliding, the contact points on its surface, do not get enough time to lock into the contact points of the other surface.
The threaded tyres of cars, trucks and bus
- a)Decrease friction of ground
- b)Increase the velocity of vehicles
- c)Increase the diameter
- d)To increase friction and to give a better grip to them on the road
Correct answer is option 'D'. Can you explain this answer?
The threaded tyres of cars, trucks and bus
a)
Decrease friction of ground
b)
Increase the velocity of vehicles
c)
Increase the diameter
d)
To increase friction and to give a better grip to them on the road
|
Pooja Shah answered |
The treaded tyres of cars, trucks and bulldozers increase friction force between road and tyres and provide a better grip with the ground.
Friction is the resistance to motion of one object moving relative to another.
Friction is a resultant force not a fundamental one like the electromagnetic force.
Friction is the resistance to motion of one object moving relative to another.
Friction is a resultant force not a fundamental one like the electromagnetic force.
If a body moves on the sandy surface, its motion will
- a)Increase
- b)Decrease
- c)Neither increase nor decrease
- d)None of these
Correct answer is option 'B'. Can you explain this answer?
If a body moves on the sandy surface, its motion will
a)
Increase
b)
Decrease
c)
Neither increase nor decrease
d)
None of these
|
|
Kavya Mishra answered |
If a body moves on a sandy surface, its motion will generally decrease (option b).
This is because the sandy surface creates more friction and resistance compared to smoother surfaces, making it harder for the body to move. The increased friction slows down the body's motion.
Smooth surface has- a) less frictional force
- b) more frictional force
- c) sometimes less and sometimes more force
- d) all the above.
Correct answer is option 'A'. Can you explain this answer?
Smooth surface has
a)
less frictional force
b)
more frictional force
c)
sometimes less and sometimes more force
d)
all the above.
|
Shruti Choudhury answered |
**Explanation:**
**Friction** is the force that opposes the relative motion between two surfaces in contact. It acts tangentially to the surface and has two types: static friction and kinetic friction.
**Static friction** is the force that prevents a stationary object from moving when a force is applied to it. It is directly proportional to the force applied and can vary in magnitude. The maximum static friction force that can be exerted is given by the equation:
**fs ≤ µsN**
where fs is the static friction force, µs is the coefficient of static friction, and N is the normal force exerted on the object.
**Kinetic friction** is the force that opposes the sliding motion between two surfaces in contact. It is generally smaller than the maximum static friction force and is given by the equation:
**fk = µkN**
where fk is the kinetic friction force, µk is the coefficient of kinetic friction, and N is the normal force exerted on the object.
**Smooth surfaces** have a low coefficient of friction, meaning they have less resistance to motion and therefore experience less frictional force compared to rough surfaces.
Now, let's consider the options given:
**a) Less frictional force:** Smooth surfaces have less frictional force because their coefficients of friction (both static and kinetic) are low. This means that it is easier for objects to slide or move on smooth surfaces with less resistance.
**b) More frictional force:** This option is incorrect because, as mentioned above, smooth surfaces have less frictional force due to their low coefficients of friction.
**c) Sometimes less and sometimes more force:** This option is incorrect because smooth surfaces consistently have less frictional force compared to rough surfaces.
**d) All of the above:** This option is incorrect as well because only option 'a' is correct.
Therefore, the correct answer is option 'A', smooth surfaces have less frictional force.
**Friction** is the force that opposes the relative motion between two surfaces in contact. It acts tangentially to the surface and has two types: static friction and kinetic friction.
**Static friction** is the force that prevents a stationary object from moving when a force is applied to it. It is directly proportional to the force applied and can vary in magnitude. The maximum static friction force that can be exerted is given by the equation:
**fs ≤ µsN**
where fs is the static friction force, µs is the coefficient of static friction, and N is the normal force exerted on the object.
**Kinetic friction** is the force that opposes the sliding motion between two surfaces in contact. It is generally smaller than the maximum static friction force and is given by the equation:
**fk = µkN**
where fk is the kinetic friction force, µk is the coefficient of kinetic friction, and N is the normal force exerted on the object.
**Smooth surfaces** have a low coefficient of friction, meaning they have less resistance to motion and therefore experience less frictional force compared to rough surfaces.
Now, let's consider the options given:
**a) Less frictional force:** Smooth surfaces have less frictional force because their coefficients of friction (both static and kinetic) are low. This means that it is easier for objects to slide or move on smooth surfaces with less resistance.
**b) More frictional force:** This option is incorrect because, as mentioned above, smooth surfaces have less frictional force due to their low coefficients of friction.
**c) Sometimes less and sometimes more force:** This option is incorrect because smooth surfaces consistently have less frictional force compared to rough surfaces.
**d) All of the above:** This option is incorrect as well because only option 'a' is correct.
Therefore, the correct answer is option 'A', smooth surfaces have less frictional force.
The shape of fish is streamlined to- a)Change the direction
- b)Increase fluid friction
- c)Facilitate breathing
- d)Decrease fluid friction
Correct answer is option 'D'. Can you explain this answer?
The shape of fish is streamlined to
a)
Change the direction
b)
Increase fluid friction
c)
Facilitate breathing
d)
Decrease fluid friction
|
Sumit Bansal answered |
This is because when a object is streamlined it cuts the upon itself by fluids through streamline shape
What is a spring balance used for?- a)Measuring weight
- b)Measuring mass
- c)Measuring force
- d)Measuring speed
Correct answer is option 'C'. Can you explain this answer?
What is a spring balance used for?
a)
Measuring weight
b)
Measuring mass
c)
Measuring force
d)
Measuring speed
|
EduRev Class 8 answered |
A spring balance is used for measuring force.
- Working Principle: It operates on Hooke's Law, which states that the force exerted by a spring is directly proportional to the displacement of the spring.
- Usage: When an object is attached, the spring stretches, and the amount of stretch correlates with the force applied, which is often related to the object's weight.
- Units: Typically measures force in newtons (N).
Hence, the correct answer is C: Measuring force.
- Working Principle: It operates on Hooke's Law, which states that the force exerted by a spring is directly proportional to the displacement of the spring.
- Usage: When an object is attached, the spring stretches, and the amount of stretch correlates with the force applied, which is often related to the object's weight.
- Units: Typically measures force in newtons (N).
Hence, the correct answer is C: Measuring force.
Why is it easier to move a box already in motion than to start moving it?- a)Less gravitational force
- b)Less static friction
- c)More kinetic energy
- d)Less air resistance
Correct answer is option 'B'. Can you explain this answer?
a)
Less gravitational force
b)
Less static friction
c)
More kinetic energy
d)
Less air resistance
|
Mehul Malik answered |
Understanding Friction in Motion
Moving a box requires overcoming forces that resist its movement. The primary reason it is easier to move a box already in motion than to start moving it is due to the differences in frictional forces involved.
Types of Friction
- Static Friction: This is the friction that must be overcome to start moving an object at rest. It is usually higher than kinetic friction.
- Kinetic Friction: Once the object is in motion, it experiences kinetic friction, which is generally lower than static friction.
Why is Option B Correct?
- Less Static Friction: When an object is stationary, static friction acts to keep it at rest. This force can be significant and varies depending on the materials in contact. It requires a greater applied force to overcome this static friction and initiate movement.
- Once in Motion: Once the box is moving, it transitions to kinetic friction. Kinetic friction is easier to overcome because it is less than static friction.
Implications of Kinetic Energy
- Energy Considerations: An object in motion has kinetic energy, which means it will continue to move unless acted upon by another force. Thus, once the box is in motion, it requires less energy to maintain that motion compared to the energy needed to start it.
Conclusion
In summary, the reason it is easier to move a box already in motion than to start moving it is primarily due to the lower kinetic friction that acts on a moving object compared to the higher static friction that must be overcome to initiate movement.
Moving a box requires overcoming forces that resist its movement. The primary reason it is easier to move a box already in motion than to start moving it is due to the differences in frictional forces involved.
Types of Friction
- Static Friction: This is the friction that must be overcome to start moving an object at rest. It is usually higher than kinetic friction.
- Kinetic Friction: Once the object is in motion, it experiences kinetic friction, which is generally lower than static friction.
Why is Option B Correct?
- Less Static Friction: When an object is stationary, static friction acts to keep it at rest. This force can be significant and varies depending on the materials in contact. It requires a greater applied force to overcome this static friction and initiate movement.
- Once in Motion: Once the box is moving, it transitions to kinetic friction. Kinetic friction is easier to overcome because it is less than static friction.
Implications of Kinetic Energy
- Energy Considerations: An object in motion has kinetic energy, which means it will continue to move unless acted upon by another force. Thus, once the box is in motion, it requires less energy to maintain that motion compared to the energy needed to start it.
Conclusion
In summary, the reason it is easier to move a box already in motion than to start moving it is primarily due to the lower kinetic friction that acts on a moving object compared to the higher static friction that must be overcome to initiate movement.
Friction always- a)helps the motion
- b)opposes the motion
- c)both of these
- d)none of these.
Correct answer is option 'B'. Can you explain this answer?
Friction always
a)
helps the motion
b)
opposes the motion
c)
both of these
d)
none of these.
|
Deebyajyoti answered |
The force which opposes the motion of an object is called frictional force and frictional force always act in a direction opposite to the direction of motion of the object.
What increases the force of friction between two surfaces?- a)Decreasing pressure
- b)Increasing pressure
- c)Reducing contact area
- d)Reducing surface area
Correct answer is option 'B'. Can you explain this answer?
a)
Decreasing pressure
b)
Increasing pressure
c)
Reducing contact area
d)
Reducing surface area
|
Master Training Institute answered |
Increasing the pressure between two surfaces increases the interlocking of irregularities, thereby increasing friction.
What is the effect of friction when a jar of a mixer is operated?- a)It increases speed
- b)It reduces efficiency
- c)It generates heat
- d)It decreases weight
Correct answer is option 'C'. Can you explain this answer?
a)
It increases speed
b)
It reduces efficiency
c)
It generates heat
d)
It decreases weight
|
Lohit Matani answered |
Friction between the moving parts generates heat, causing the jar of the mixer to become hot.
Objects moving through fluids experience _______ force.- a)Magnetic
- b)Gravitational
- c)Frictional
- d)Elastic
Correct answer is option 'C'. Can you explain this answer?
Objects moving through fluids experience _______ force.
a)
Magnetic
b)
Gravitational
c)
Frictional
d)
Elastic
|
S.S Career Academy answered |
When objects move through fluids like air or water, they experience a force called frictional force. This force makes it harder for objects to move smoothly through the fluid.
Friction is a/an- a)Friend
- b)Foe
- c)Both (a) and (b)
- d)None.
Correct answer is option 'C'. Can you explain this answer?
Friction is a/an
a)
Friend
b)
Foe
c)
Both (a) and (b)
d)
None.
|
Meera Basu answered |
Friction is both friend as well as foe.
Friend:- as friction helps us to write, walk to control our speed .
Foe:- as it cause wear and tear in object.
So, friction is both Friend and foe.
Friend:- as friction helps us to write, walk to control our speed .
Foe:- as it cause wear and tear in object.
So, friction is both Friend and foe.
Why do we slip when we step on a banana peel?- a)Increased gravitational pull
- b)Reduced friction
- c)Increased air resistance
- d)Reduced weight
Correct answer is option 'B'. Can you explain this answer?
a)
Increased gravitational pull
b)
Reduced friction
c)
Increased air resistance
d)
Reduced weight
|
Academic Studio answered |
The banana peel reduces the friction between our feet and the ground, making it easier to slip.
What helps increase the grip of a shoe on the floor?- a)Smooth soles
- b)Grooved soles
- c)Thin soles
- d)Heavy soles
Correct answer is option 'B'. Can you explain this answer?
a)
Smooth soles
b)
Grooved soles
c)
Thin soles
d)
Heavy soles
|
T.S Academy answered |
Grooved soles provide better grip on the floor by increasing friction.
We slip while walking on a path having pond scum or green algae because: - a)The inertia of motion
- b)The friction is zero
- c)The friction between the feet and the path is increased.
- d)The friction between the feet and the path is reduced.
Correct answer is option 'D'. Can you explain this answer?
We slip while walking on a path having pond scum or green algae because:
a)
The inertia of motion
b)
The friction is zero
c)
The friction between the feet and the path is increased.
d)
The friction between the feet and the path is reduced.
|
|
Shanaya Menon answered |
Why we slip while walking on a path with pond scum or green algae?
The correct answer is option 'D', which states that the friction between the feet and the path is reduced. Let's understand why this is the correct answer in detail.
The concept of friction:
Friction is the force that opposes the relative motion between two surfaces in contact. It plays a crucial role in our daily lives, allowing us to walk, hold objects, and perform various tasks requiring grip.
Factors affecting friction:
Friction depends on several factors, including the nature of the surfaces in contact and the force pressing them together. When there is an increase in the roughness of the surfaces or an increase in the force pressing them together, the friction between the surfaces also increases.
Effect of pond scum or green algae on friction:
When we walk on a path covered with pond scum or green algae, the surface becomes slimy and slippery. This slimy layer reduces the friction between our feet and the path, making it easier for us to slip.
1. Reduction in surface roughness: Pond scum or green algae create a slimy layer on the path, which reduces the roughness of the surface. The slimy layer acts as a lubricant, making it difficult for our feet to grip onto the surface.
2. Reduction in force pressing the surfaces together: As we step on the slimy surface, the force pressing our feet against the path decreases due to the lubricating effect of the pond scum or green algae. This reduced force diminishes the friction between our feet and the path, further increasing the chances of slipping.
Consequences of reduced friction:
When the friction between our feet and the path is reduced, we experience a lack of grip and stability. This can lead to slipping and loss of balance, which can cause falls, injuries, and accidents.
In summary, the presence of pond scum or green algae on a path reduces the friction between our feet and the surface. The slimy layer acts as a lubricant, decreasing the surface roughness and the force pressing the surfaces together. This reduction in friction makes it easier for us to slip while walking on such a path.
The correct answer is option 'D', which states that the friction between the feet and the path is reduced. Let's understand why this is the correct answer in detail.
The concept of friction:
Friction is the force that opposes the relative motion between two surfaces in contact. It plays a crucial role in our daily lives, allowing us to walk, hold objects, and perform various tasks requiring grip.
Factors affecting friction:
Friction depends on several factors, including the nature of the surfaces in contact and the force pressing them together. When there is an increase in the roughness of the surfaces or an increase in the force pressing them together, the friction between the surfaces also increases.
Effect of pond scum or green algae on friction:
When we walk on a path covered with pond scum or green algae, the surface becomes slimy and slippery. This slimy layer reduces the friction between our feet and the path, making it easier for us to slip.
1. Reduction in surface roughness: Pond scum or green algae create a slimy layer on the path, which reduces the roughness of the surface. The slimy layer acts as a lubricant, making it difficult for our feet to grip onto the surface.
2. Reduction in force pressing the surfaces together: As we step on the slimy surface, the force pressing our feet against the path decreases due to the lubricating effect of the pond scum or green algae. This reduced force diminishes the friction between our feet and the path, further increasing the chances of slipping.
Consequences of reduced friction:
When the friction between our feet and the path is reduced, we experience a lack of grip and stability. This can lead to slipping and loss of balance, which can cause falls, injuries, and accidents.
In summary, the presence of pond scum or green algae on a path reduces the friction between our feet and the surface. The slimy layer acts as a lubricant, decreasing the surface roughness and the force pressing the surfaces together. This reduction in friction makes it easier for us to slip while walking on such a path.
What does the reading on a spring balance indicate when a brick begins to move?- a)Weight of the brick
- b)Force of friction
- c)Mass of the brick
- d)Gravitational force
Correct answer is option 'B'. Can you explain this answer?
a)
Weight of the brick
b)
Force of friction
c)
Mass of the brick
d)
Gravitational force
|
Upsc Rank Holders answered |
The reading on the spring balance gives a measure of the force of friction between the brick and the floor when the brick just begins to move.
Friction increases with increase in the smoothness of the surface.- a)True
- b)False
Correct answer is option 'B'. Can you explain this answer?
Friction increases with increase in the smoothness of the surface.
a)
True
b)
False
|
Nancy yadav answered |
It's answer is false because as the smoothness increases friction decreases
State whether the following statement is True or FalseFriction always acts in the same direction as the applied force.- a)True
- b)False
Correct answer is option 'B'. Can you explain this answer?
State whether the following statement is True or False
Friction always acts in the same direction as the applied force.
a)
True
b)
False
|
Future Foundation Institute answered |
- When we push or pull an object, friction acts in the opposite direction to the motion. So, if we push a book to the right, friction acts to the left, and if we push it to the left, friction acts to the right. This means friction opposes the motion, trying to stop the object from moving. So, the statement is False.
- Imagine you are playing with your toy car. If you give it a push, it moves forward, but if you push it backward, it moves in that direction instead. Friction works in a way that always tries to slow down or stop things from moving too easily.
Friction is caused by the irregularities on the two __________ in contact.- a)Different
- b)Surfaces
- c)Smooth
- d)Heavy
Correct answer is option 'B'. Can you explain this answer?
Friction is caused by the irregularities on the two __________ in contact.
a)
Different
b)
Surfaces
c)
Smooth
d)
Heavy
|
|
Lohit Matani answered |
Friction is caused by the irregularities on the two surfaces in contact. This means that when two things are touching each other, the bumps and rough parts on their surfaces stick together, making it harder to move them against each other. So, the correct answer is "Surfaces."
How does the smoothness of surfaces affect friction?- a)It has no effect
- b)Smoother surfaces increase friction
- c)Smoother surfaces decrease friction
- d)It depends on the material
Correct answer is option 'C'. Can you explain this answer?
a)
It has no effect
b)
Smoother surfaces increase friction
c)
Smoother surfaces decrease friction
d)
It depends on the material
|
Abhijeet Kumar answered |
Impact of Surface Smoothness on Friction:
Friction is the force that resists the motion of one surface over another. The smoothness of surfaces plays a crucial role in determining the amount of friction generated between them.
Effect of Smoother Surfaces on Friction:
- Smoother surfaces generally decrease friction between them.
- This is because smoother surfaces have fewer irregularities or rough patches that could create resistance when sliding over each other.
- The contact between two smooth surfaces is more uniform, resulting in less frictional force.
Explanation:
- When two surfaces are rough, the irregularities on the surfaces interlock with each other, creating more friction and making it harder for the surfaces to slide past each other.
- On the other hand, smooth surfaces have fewer points of contact, reducing the frictional force between them.
- This is why smoother surfaces typically experience less friction compared to rough surfaces.
Material Dependency:
- It is important to note that the impact of surface smoothness on friction can also depend on the materials involved.
- For example, even if two surfaces are smooth, certain materials may still exhibit high levels of friction due to their inherent properties.
- Therefore, while smoother surfaces generally decrease friction, the specific material properties must also be considered when analyzing the overall frictional behavior.
In conclusion, smoother surfaces tend to decrease friction between them by promoting more uniform contact and reducing surface irregularities that could create resistance. However, material properties can also influence the overall frictional behavior, highlighting the complex nature of friction in different scenarios.
Friction is the force that resists the motion of one surface over another. The smoothness of surfaces plays a crucial role in determining the amount of friction generated between them.
Effect of Smoother Surfaces on Friction:
- Smoother surfaces generally decrease friction between them.
- This is because smoother surfaces have fewer irregularities or rough patches that could create resistance when sliding over each other.
- The contact between two smooth surfaces is more uniform, resulting in less frictional force.
Explanation:
- When two surfaces are rough, the irregularities on the surfaces interlock with each other, creating more friction and making it harder for the surfaces to slide past each other.
- On the other hand, smooth surfaces have fewer points of contact, reducing the frictional force between them.
- This is why smoother surfaces typically experience less friction compared to rough surfaces.
Material Dependency:
- It is important to note that the impact of surface smoothness on friction can also depend on the materials involved.
- For example, even if two surfaces are smooth, certain materials may still exhibit high levels of friction due to their inherent properties.
- Therefore, while smoother surfaces generally decrease friction, the specific material properties must also be considered when analyzing the overall frictional behavior.
In conclusion, smoother surfaces tend to decrease friction between them by promoting more uniform contact and reducing surface irregularities that could create resistance. However, material properties can also influence the overall frictional behavior, highlighting the complex nature of friction in different scenarios.
Which substance is commonly sprinkled on a carrom board to reduce friction?- a)Water
- b)Oil
- c)Powder
- d)Sand
Correct answer is option 'C'. Can you explain this answer?
Which substance is commonly sprinkled on a carrom board to reduce friction?
a)
Water
b)
Oil
c)
Powder
d)
Sand
|
Trisha Vashisht answered |
Powder is sprinkled on the surface of a carrom board to reduce friction, allowing smoother and faster movement of the striker and carrom men.
Which of the following is used to measure the force of friction between two surfaces?- a)Thermometer
- b)Barometer
- c)Spring balance
- d)Speedometer
Correct answer is option 'C'. Can you explain this answer?
Which of the following is used to measure the force of friction between two surfaces?
a)
Thermometer
b)
Barometer
c)
Spring balance
d)
Speedometer
|
|
EduRev Class 8 answered |
A spring balance is used to measure the force of friction by indicating the force required to start moving an object or keep it moving.
What is the primary role of friction in the context of moving objects?- a)It accelerates the objects
- b)It opposes the motion of the objects
- c)It changes the direction of motion
- d)It has no effect on the objects
Correct answer is option 'B'. Can you explain this answer?
What is the primary role of friction in the context of moving objects?
a)
It accelerates the objects
b)
It opposes the motion of the objects
c)
It changes the direction of motion
d)
It has no effect on the objects
|
|
EduRev Class 8 answered |
Friction always acts to oppose the relative motion between two surfaces in contact, slowing down moving objects.
What type of friction occurs when one body rolls over the surface of another body?- a)Static friction
- b)Kinetic friction
- c)Rolling friction
- d)Fluid friction
Correct answer is option 'C'. Can you explain this answer?
a)
Static friction
b)
Kinetic friction
c)
Rolling friction
d)
Fluid friction
|
|
Lohit Matani answered |
Rolling friction occurs when one body rolls over the surface of another body, reducing the resistance compared to sliding friction.
Why is it difficult to walk on a wet floor without slipping?- a)Increased gravitational pull
- b)Reduced friction
- c)Increased air resistance
- d)Reduced weight
Correct answer is option 'B'. Can you explain this answer?
Why is it difficult to walk on a wet floor without slipping?
a)
Increased gravitational pull
b)
Reduced friction
c)
Increased air resistance
d)
Reduced weight
|
Coders Trust answered |
- When a floor is wet, water creates a thin layer between your shoes and the surface.
- This layer reduces the contact area, which is essential for grip.
- Friction is the force that helps our feet push against the ground to maintain balance.
- With decreased friction on a wet surface, it’s easier to slip, making walking more difficult and potentially dangerous.
- Thus, the primary reason for difficulty is reduced friction, not changes in weight or gravitational pull.
- This layer reduces the contact area, which is essential for grip.
- Friction is the force that helps our feet push against the ground to maintain balance.
- With decreased friction on a wet surface, it’s easier to slip, making walking more difficult and potentially dangerous.
- Thus, the primary reason for difficulty is reduced friction, not changes in weight or gravitational pull.
Why is it easier to pull luggage fitted with rollers?- a)Rollers reduce weight.
- b)Rollers reduce friction.
- c)Rollers eliminate gravity.
- d)Rollers increase speed.
Correct answer is option 'B'. Can you explain this answer?
a)
Rollers reduce weight.
b)
Rollers reduce friction.
c)
Rollers eliminate gravity.
d)
Rollers increase speed.
|
Upsc Toppers answered |
Rollers reduce friction by converting sliding friction to rolling friction, making it easier to pull luggage.
Chapter doubts & questions for Friction - Physics 2025 is part of Grade 9 exam preparation. The chapters have been prepared according to the Grade 9 exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for Grade 9 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.
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