The Class 8 Physics Chapter 3 – Force and Pressure, deal with the topic of force and pressure in detail. The ICSE Selina Class 8 Physics Chapter 3 – Force and Pressure Solutions have a collective extract from various subject related books, making it the most efficient resource for students studying it.
Force: A push or a pull is known as force. Whenever force is applied, 2 objects are involved- the object applying the force and the object receiving the force. The chapter deals with the effect of force and also the direction and magnitude of force. The chapter also discusses the types of forces:
- Contact force:
- Muscular force
- Friction force
- Non-contact force
- Magnetic force
- Electrostatic force
- Gravitational force
Pressure: The force acting per unit area is known as pressure.
Pressure=force/area
The chapter discusses on the pressure exerted by the liquid and gas. The chapter additionally explains about the atmospheric pressure. Go through the chapter thoroughly at first and later try solving the Selina questions. Compare your answers with the ICSE Selina Class 8 Physics Chapter 3 – Force and Pressure solutions by BYJU’S and evaluate your preparation so far.
Download ICSE Class 8 Physics Selina Solutions PDF for Chapter 3 – Force and Pressure
A. Objective Questions
Question 1
Write true or false for each statement
(a) The S.I. unit of force is kgf.
Answer: False.
(b) A force always produces both the linear and turning motions.
Answer: False.
(c) Moment of force = force × perpendicular distance of force – from the pivoted point.
Answer: True.
(d) Less force is needed when applied at a farther distance from the pivoted point.
Answer: True.
(e) For a given thrust, pressure is more on a surface of large j area.
Answer: False.
(f) The pressure on a surface increases with an increase in the thrust on the surface.
Solution: True.
(g) A man exerts the same pressure on the ground whether he is standing or he is lying.
Answer: False.
(h) It is easier to hammer a blunt nail into a piece of wood than a sharply pointed nail.
Answer: False.
(i) The S.L. unit of pressure is the pascal.
Answer: True.
(j) Water in a lake exerts pressure only at its bottom.
Answer: False.
(k) A liquid exerts pressure in all directions.
Answer: True.
(l) Gases exert pressure in all directions.
Answer: True.
(m) The atmospheric pressure is nearly Pa.
Answer: True.
(n) Higher we go, the greater the air pressure.
Answer: False.
Question 2
Fill in the blanks
(a) 1 kgf = 10 N (nearly)
(b) Moment of force = force × distance of force from the point of turning
(c) In a door, handle is provided farthest from the hinges.
(d) The unit of thrust is newton.
(e) Thrust is the normal force acting on a surface.
(f) Pressure is the thrust acting on a surface of unit area.
(g) The unit of pressure is the pascal
(h) Pressure is reduced if the area of surface increases.
(i) Pressure in a liquid increases with the depth.
(j) The atmospheric pressure on the earth’s surface is nearly 10Â 5Pa.
Question 3
Match the following:
Column AÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Column B
(a) Camel                           (i) broad and deep foundation
(b) Truck                            (ii) broad feet
(c) Knife                            (iii) six or eight tyres
(d) High building                    (iv) sharp cutting edge
(e) Thrust                           (v) atm
(f) Moment of force                  (vi) N
(g) Atmospheric pressure             (vii) N m
Solution:
Column AÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Column B
(a) Camel                         (ii) broad feet
(b) Truck                         (iii) six or eight tyres
(c) Knife                         (iv) sharp cutting edge
(d) High building                 (i) broad and deep foundation
(e) Thrust                       (vi) N
(f) Moment of force              (vii) N m
(g) Atmospheric pressure          (v) atm
Question 4
Select the correct alternative:
(a) SI. unit of moment of force is
1. N
2. N cm
3. kgfm
4. N m
Solution:Â The correct answer is 4. N m
(b) To obtain a given moment of force for turning a body, the force needed can be decreased by
1. applying the force at the pivoted point
2. applying the force very close to the pivoted point
3. applying the force farthest from the pivoted point
4. none of the above
Solution: The correct answer is 3. applying the force farthest from the pivoted point
(c) The unit of thrust is
1. kgf
2. kg
3. g
4. ms-1
Solution:Â Â The correct answer is 1. kgf
(d) The unit of pressure is
1. N×m
2. kgf
3. N
4. kgf
Solution:  The correct answer is 3. N
(e) The pressure and thrust are related as
1. Pressure = Thrust
2. Pressure = Thrust x Area
3. Pressure = Thrust/Area
4. Pressure = Area/Thrust
Solution:Â Â Â The correct answer is 3. Pressure = Thrust/Area
(f) A body weighing 5 kgf, placed on a surface of area 0.1 m2 exerts a thrust on the surface equal to
1. 50 kgf
2. 5 kgf
3. 50 kgf
4. 5 kgf
Solution:  The correct answer is 3. 50 kgf
(g) The feet of lizards act like
1. moving pads
2. drilling pads
3. suction pads
4. none of the above
Solution: The correct answer is 3. suction pads
(h) The pressure exerted by a liquid is due to its
1. weight
2. mass
3. volume
4. area
Solution: The correct answer is 1. weight
(i) Pressure inside a liquid increases with:
1. increase in depth
2. decrease in depth
3. decrease in density
4. none of the above
Solution: The correct answer is 1. increase in depth
(j) The atmospheric pressure at sea level is nearly
1. 10 Pa
2. 100,000 Pa
3. 100 Pa
4. 10,000 Pa
Solution: The correct answer is 2. 100,000 Pa
(k) Nose bleeding may occur at a high altitude because
1. the atmospheric pressure decreases
2. the oxygen content of the atmosphere decreases
3. the atmospheric pressure increases
4. there are strong air currents at the high altitude
Solution: The correct answer is 1. the atmospheric pressure decreases
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