Q1: What is force? (a) A push or pull acting on a body (b) The weight of an object only (c) The speed of a moving object (d) The distance travelled by an object
Solution:
Ans: (a) Force is defined as a push or pull that can cause different effects on a body, including motion changes and shape changes.
Q2: Why does a nail have a sharp pointed end? (a) To make it look attractive (b) Small area creates high pressure (c) To increase its weight (d) Large area creates low pressure
Solution:
Ans: (b) A sharp pointed end has a small area of contact, which creates high pressure on the surface, making penetration easier.
Q3: What is the SI unit of moment of force? (a) Newton (b) Pascal (c) Newton metre (d) Kilogram
Solution:
Ans: (c) The SI unit of moment of force is newton metre because moment is calculated as force in newtons multiplied by distance in metres.
Q4: One kilogram force (1 kgf) equals how many newtons approximately? (a) 1 N (b) 5 N (c) 10 N (d) 100 N
Solution:
Ans: (c) One kilogram force equals approximately ten newtons, which is the relationship between gravitational and SI units of force used commonly.
Q5: Which factor does NOT affect the turning effect of a force on a body? (a) Magnitude of the force (b) Mass of the body (c) Distance from the pivot point (d) Direction of the force
Solution:
Ans: (b) The turning effect depends on force magnitude and perpendicular distance from pivot, not on the mass of the body being turned.
Fill in the Blanks
Q1: Force is measured by its magnitude and _____.
Solution:
Ans: direction
Q2: The SI unit of pressure is newton per square metre, also called _____.
Solution:
Ans: pascal
Q3: Pressure is defined as force divided by _____.
Solution:
Ans: area
Q4: Atmospheric pressure at sea level equals _____ centimetres of mercury column.
Solution:
Ans: 76
Q5: The fixed point around which a body turns when force is applied is called the _____.
Solution:
Ans: pivot point
True or False
Q1: Force can change the speed of a moving body.
Solution:
Ans: True Force can make a moving body go faster or slower by changing its speed in either direction.
Q2: Pressure increases when the area of contact increases.
Solution:
Ans: False When area increases, the same force spreads over larger surface, reducing the pressure exerted on that surface.
Q3: The SI unit of force is newton.
Solution:
Ans: True Newton is the SI unit of force, named after scientist Sir Isaac Newton who studied force extensively.
Q4: Liquid pressure acts only on the bottom of the container.
Solution:
Ans: False Liquids exert pressure in all directions, not just on the bottom but also on the sides of containers.
Q5: Atmospheric pressure decreases at higher altitudes.
Solution:
Ans: True At higher altitudes, air becomes thinner with less weight above, resulting in lower atmospheric pressure than at sea level.
Match the Following
Solution:
Ans:
1 - E: Newton metre is the SI unit used to measure the moment of force acting on a rotating body.
2 - C: Pascal is the SI unit of pressure, which equals one newton per square metre of surface area.
3 - D: One kilogram force approximately equals ten newtons, showing the relationship between gravitational and SI units of force.
4 - B: Moment of force is calculated by multiplying the force by its perpendicular distance from the pivot point.
5 - A: At sea level, atmospheric pressure equals the pressure exerted by a 76 centimetre column of mercury in a tube.
Short Answer Questions
Q1: Explain three effects of force on a body.
Solution:
Ans: Force can make a body at rest start moving or stop a moving body. It can change the speed of a moving body, making it faster or slower. Force can also change the direction of a moving body. Additionally, force can change the size or shape of a body if it cannot move freely.
Q2: Why do heavy trucks have more tyres than ordinary vehicles?
Solution:
Ans: Heavy trucks have six to eight tyres instead of four because more tyres increase the contact area with the ground. When the contact area increases, the pressure on the ground decreases. This prevents the truck from sinking into the ground and helps it move smoothly, especially on soft surfaces like mud or sand.
Q3: Define pressure and state its SI unit.
Solution:
Ans: Pressure is defined as the thrust or force acting per unit area of a surface. The formula for pressure is P equals F divided by A, where P is pressure, F is force, and A is area. The SI unit of pressure is newton per square metre, also called pascal, abbreviated as Pa.
Q4: What is moment of force? On what factors does it depend?
Solution:
Ans: Moment of force is the turning effect of a force on a body that rotates around a pivot point. It equals force multiplied by perpendicular distance from the pivot. It depends on two factors: the magnitude of the force applied and the perpendicular distance of force from the pivot point where it acts.
Q5: Explain why dams are built thicker at the base.
Solution:
Ans: Dams are built thicker at the base because liquid pressure increases with height of the liquid column. At greater depths, water exerts more pressure on dam walls. To withstand high pressure at the bottom, dams need stronger and thicker construction at base. This prevents the dam from breaking under high water pressure at depth.
The document Worksheet with Solutions: Force and Pressure is a part of the Class 8 Course Physics Class 8 ICSE.
FAQs on Worksheet with Solutions: Force and Pressure
1. What is the definition of force?
Ans. Force is defined as an interaction that causes an object to change its velocity, which can include starting, stopping, or changing direction. It is measured in newtons (N).
2. How is pressure calculated?
Ans. Pressure is calculated by dividing the force applied perpendicular to the surface by the area over which the force is distributed. The formula is Pressure = Force/Area.
3. What are the units of pressure?
Ans. The SI unit of pressure is the pascal (Pa), which is equivalent to one newton per square metre (N/m²). Other common units include atmospheres (atm) and millimetres of mercury (mmHg).
4. How does increasing the area affect pressure?
Ans. Increasing the area over which a force is applied decreases the pressure. This is because pressure is inversely proportional to area; if the force remains constant, a larger area results in a lower pressure.
5. What is the relationship between force and pressure in everyday examples?
Ans. In everyday examples, such as walking on snow, a person exerts a force on the ground. If they wear snowshoes, which increase the area of contact, the pressure on the snow is reduced, preventing them from sinking.
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