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All questions of Exploring Forces for Class 8 Exam

Which of the following is NOT a contact force?
  • a)
    Tension
  • b)
    Friction
  • c)
    Gravitational force
  • d)
    Muscular force
Correct answer is option 'C'. Can you explain this answer?

Emily Wong answered
Understanding Contact Forces
In physics, forces can be classified into two main types: contact forces and non-contact forces. Contact forces occur when objects physically touch each other, while non-contact forces act at a distance without physical contact.
Contact Forces Explained
- Tension: This is a force transmitted through a string, rope, or wire when it is pulled tight by forces acting from opposite ends. It is a classic example of a contact force.
- Friction: This force opposes the motion of an object when it is in contact with another surface. It arises from the interaction between the surfaces and is therefore a contact force.
- Muscular Force: This is the force exerted by muscles when they contract. When a person pushes or pulls an object, this force is applied through direct contact, making it a contact force.
Gravitational Force as a Non-Contact Force
- Gravitational Force: Unlike the others, gravitational force acts at a distance. It is the attraction between two masses, such as the Earth and an object. This force does not require physical contact to exist; it operates through the gravitational field.
Conclusion
In summary, the correct answer to the question is option 'C', the gravitational force, as it is a non-contact force, while the others—tension, friction, and muscular force—are all contact forces that require direct interaction between objects. Understanding these distinctions is fundamental in the study of physics and mechanics.
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How does friction affect the motion of an object?
  • a)
    It always slows down the object
  • b)
    It always speeds up the object
  • c)
    It has no effect on the object
  • d)
    It can either speed up or slow down the object
Correct answer is option 'A'. Can you explain this answer?

C K Academy answered
Friction always acts in the opposite direction to the motion of an object, which means it will slow down the object. This resistance is due to the interactions between the surfaces in contact. For example, a box sliding on a rough surface will come to a stop quicker than on a smooth surface due to greater friction.

What happens to an object's mass when it is moved from Earth to the Moon?
  • a)
    It becomes zero
  • b)
    It increases
  • c)
    It remains the same
  • d)
    It decreases
Correct answer is option 'C'. Can you explain this answer?

Clifford Academy answered
An object's mass remains the same regardless of its location, whether on Earth, the Moon, or any other planet. Mass is a measure of the amount of matter in an object and does not change with gravitational influence.

How do static charges interact when two like-charged objects are brought close together?
  • a)
    They repel each other
  • b)
    They attract each other
  • c)
    They remain unaffected
  • d)
    They create a magnetic field
Correct answer is option 'A'. Can you explain this answer?

Clifford Academy answered
Like-charged objects repel each other when brought close together. This is a principle of electrostatics, where similar charges repel and opposite charges attract. This property is fundamental in understanding electrical interactions and applications.

How does the nature of surfaces affect friction?
  • a)
    Friction is unaffected by surface nature
  • b)
    Smoother surfaces have more friction
  • c)
    Rougher surfaces have less friction
  • d)
    Rougher surfaces have more friction
Correct answer is option 'D'. Can you explain this answer?

Clifford Academy answered
Rougher surfaces have more friction because the irregularities in the surfaces interlock more effectively, resisting motion. This is why objects slide more easily on smooth surfaces compared to rough ones. This concept is vital in engineering and design to reduce or increase friction as needed.

What effect does applying a push force to a stationary object have?
  • a)
    It will sink
  • b)
    It will change shape
  • c)
    It will start moving
  • d)
    It will float
Correct answer is option 'C'. Can you explain this answer?

Clifford Academy answered
Applying a push force to a stationary object will cause it to start moving. This is an example of how force can change the state of an object from rest to motion. This principle is foundational in physics, as it demonstrates the relationship between force and motion.

What principle explains why a ship floats on water?
  • a)
    Archimedes' Principle
  • b)
    Conservation of Momentum
  • c)
    Bernoulli's Principle
  • d)
    Newton's First Law
Correct answer is option 'A'. Can you explain this answer?

Clifford Academy answered
Archimedes' Principle explains why a ship floats on water. It states that an object immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced. If the weight of the ship is less than the weight of the water it displaces, it floats.

Which of the following is an example of a non-contact force?
  • a)
    Muscular force
  • b)
    Gravitational force
  • c)
    Tension
  • d)
    Friction
Correct answer is option 'B'. Can you explain this answer?

Clifford Academy answered
Gravitational force is a non-contact force because it acts at a distance, pulling objects toward each other without any physical contact. This force is always attractive and is responsible for the weight of objects on Earth. An interesting fact is that gravitational force acts between all masses, not just those on Earth.

Which of the following best describes the role of buoyant force?
  • a)
    It has no effect on objects in liquids
  • b)
    It pushes objects upwards in a liquid
  • c)
    It pushes objects downwards in a liquid
  • d)
    It pulls objects downwards in a liquid
Correct answer is option 'B'. Can you explain this answer?

Clifford Academy answered
Buoyant force is the upward force exerted by a liquid on an object immersed in it. This force can determine whether an object floats or sinks depending on its weight relative to the buoyant force. An interesting fact is that objects with a density less than that of the liquid will float.

What is the definition of a force in scientific terms?
  • a)
    A push or pull applied to an object
  • b)
    An object's resistance to motion
  • c)
    A measurement of energy
  • d)
    The speed of an object in motion
Correct answer is option 'A'. Can you explain this answer?

Clifford Academy answered
A force is defined as a push or pull applied to an object. It is responsible for changing the state of motion of that object, including starting, stopping, or changing its direction. Understanding this fundamental concept is crucial in physics as it explains how objects interact with one another.

What is the SI unit of force?
  • a)
    Kilogram
  • b)
    Joule
  • c)
    Newton
  • d)
    Pascal
Correct answer is option 'C'. Can you explain this answer?

Clifford Academy answered
The SI unit of force is the newton (N). It is defined as the force required to accelerate a one-kilogram mass by one meter per second squared. This unit helps in quantifying force in scientific experiments and calculations.

When two objects interact, what happens to the forces they exert on each other?
  • a)
    They are always unequal
  • b)
    They have no effect on each other
  • c)
    They cancel each other out
  • d)
    They are equal and opposite
Correct answer is option 'D'. Can you explain this answer?

Clifford Academy answered
a) They are always unequal → Incorrect. Newton’s Third Law states that forces are equal in magnitude, though they act on different objects.
b) They have no effect on each other → Incorrect. The forces exist because of interaction, so they definitely affect the motion of the objects.
c) They cancel each other out → Incorrect. The forces don’t cancel because they act on different objects. For cancellation, forces must act on the same object.
d) They are equal and opposite → Correct. Whenever two objects interact, each exerts a force on the other that is equal in size and opposite in direction (Newton’s Third Law).

What is the effect of applying brakes to a moving vehicle?
  • a)
    It increases the vehicle's speed
  • b)
    It changes the vehicle's direction
  • c)
    It has no effect on the vehicle
  • d)
    It decreases the vehicle's speed or stops it
Correct answer is option 'D'. Can you explain this answer?

Clifford Academy answered
Applying brakes to a moving vehicle decreases its speed or stops it entirely. This action involves a push force that counteracts the vehicle's motion, illustrating how force can control the movement of objects.

What is the relationship between mass and weight?
  • a)
    Weight is constant while mass varies
  • b)
    Mass only exists on Earth
  • c)
    Mass and weight are the same
  • d)
    Mass measures inertia, while weight measures gravitational force
Correct answer is option 'D'. Can you explain this answer?

Clifford Academy answered
Mass measures the amount of matter in an object and is constant regardless of location, while weight measures the gravitational force acting on that mass. Weight can change depending on the strength of the gravitational field, such as on different planets.

Which force is responsible for an object changing its shape when squeezed?
  • a)
    Muscular force
  • b)
    Magnetic force
  • c)
    Gravitational force
  • d)
    Electrostatic force
Correct answer is option 'A'. Can you explain this answer?

Clifford Academy answered
  • Muscular force: When you squeeze an object (like a rubber ball or clay), you apply pressure using your muscles. This muscular force changes its shape.
  • Magnetic force: Acts only on magnetic materials and does not change the shape of an object when you squeeze it.
  • Gravitational force: Pulls objects toward the Earth’s center. It doesn’t cause shape change during squeezing.
  • Electrostatic force: Acts between charged objects. It is not responsible for squeezing shape change.

Which of the following describes a push force?
  • a)
    Pulling a drawer open
  • b)
    Kicking a ball
  • c)
    Drawing water from a well
  • d)
    Stretching a rubber band
Correct answer is option 'B'. Can you explain this answer?

Clifford Academy answered
Kicking a ball is an example of a push force. When the foot strikes the ball, it applies a force in a specific direction, causing the ball to move. This demonstrates how force can initiate motion in an object.

Which type of force is friction classified as?
  • a)
    Gravitational force
  • b)
    Non-contact force
  • c)
    Contact force
  • d)
    Magnetic force
Correct answer is option 'C'. Can you explain this answer?

Clifford Academy answered
Friction is classified as a contact force because it arises from the interaction between two surfaces in contact. It acts to oppose the motion of an object sliding or attempting to slide over another surface, making it essential in various practical applications.

What happens to the weight of an object if it is taken to a planet with stronger gravitational force?
  • a)
    It decreases
  • b)
    It becomes zero
  • c)
    It remains the same
  • d)
    It increases
Correct answer is option 'D'. Can you explain this answer?

Clifford Academy answered
The weight of an object increases if it is taken to a planet with stronger gravitational force. Weight is directly proportional to the gravitational acceleration acting on the object. This is why astronauts weigh less on the Moon than on Earth, as the Moon's gravity is weaker.

What is the consequence of an object experiencing balanced forces?
  • a)
    It will accelerate
  • b)
    It will remain at rest or continue moving at a constant speed
  • c)
    It will change direction
  • d)
    It will change shape
Correct answer is option 'B'. Can you explain this answer?

Clifford Academy answered
When an object experiences balanced forces, it will either remain at rest or continue moving at a constant speed. This is because the net force acting on the object is zero, meaning that the forces are equal in magnitude and opposite in direction, resulting in no change in motion.

What happens to the speed of an object thrown upwards against gravity?
  • a)
    It becomes zero instantly
  • b)
    It decreases until it stops
  • c)
    It increases
  • d)
    It remains constant
Correct answer is option 'B'. Can you explain this answer?

Clifford Academy answered
The speed of an object thrown upwards against gravity decreases until it comes to a stop at its highest point. Gravity acts as a downward force, continuously opposing the upward motion until the object halts and begins to fall back down.

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