# Selina solutions for Concise Physics Class 8 ICSE chapter 3 - Force and Pressure [Latest edition]

## Chapter 3: Force and Pressure

Objective Questions [Pages 55 - 56]

### Selina solutions for Concise Physics Class 8 ICSE Chapter 3 Force and Pressure Objective Questions [Pages 55 - 56]

Objective Questions | Q 1.01 | Page 55

The S.I. unit of force is kgf. (kilogram-force)

• True

• False

Objective Questions | Q 1.02 | Page 55

A force always produces both the linear and turning motions.

• True

• False

Objective Questions | Q 1.03 | Page 55

Moment of force = force × perpendicular distance of force –  from the pivoted point.

• True

• False

Objective Questions | Q 1.04 | Page 55

Less force is needed when applied at a farther distance from the pivoted point.

• True

• False

Objective Questions | Q 1.05 | Page 55

For a given thrust, pressure is more on a surface of large j area.

• True

• False

Objective Questions | Q 1.06 | Page 55

The pressure on a surface increases with an increase in the thrust on the surface.

• True

• False

Objective Questions | Q 1.07 | Page 55

A man exerts same pressure on the ground whether he is standing or he is lying.

• True

• False

Objective Questions | Q 1.08 | Page 55

It is easier to hammer a blunt nail into a piece of wood than a sharply pointed nail.

• True

• False

Objective Questions | Q 1.09 | Page 55

The S.I. unit of pressure is pascal.

• True

• False

Objective Questions | Q 1.1 | Page 55

Water in a lake exerts pressure only at its bottom.

• True

• False

Objective Questions | Q 1.11 | Page 55

A liquid exerts pressure in all directions.

• True

• False

Objective Questions | Q 1.12 | Page 55

Gases exert pressure in all directions.

• True

• False

Objective Questions | Q 1.13 | Page 55

The atmospheric pressure is nearly 105 Pa.

• True

• False

Objective Questions | Q 1.14 | Page 55

Higher we go, greater is the air pressure.

• True

• False

Objective Questions | Q 2.01 | Page 55

1 kgf = .............. (nearly).

Objective Questions | Q 2.02 | Page 55

Moment of force =...............  × distance of force from the point of turning.

Objective Questions | Q 2.03 | Page 55

In a door, handle is provided  ......... from the hinges.

Objective Questions | Q 2.04 | Page 55

The unit of thrust is  ..........

Objective Questions | Q 2.05 | Page 55

Thrust is the ............ force acting on a surface.

Objective Questions | Q 2.06 | Page 55

Pressure is the thrust acting on a surface of ........... area.

Objective Questions | Q 2.07 | Page 55

The unit of pressure is  .........

Objective Questions | Q 2.08 | Page 55

Pressure is reduced if .................... increases.

Objective Questions | Q 2.09 | Page 55

Pressure in a liquid ................with the depth.

Objective Questions | Q 2.1 | Page 55

The atmospheric pressure on earth surface is nearly .............. .

Objective Questions | Q 3 | Page 55

Match the column

 Column A Column B (a) Camel (1) broad and deep foundation (b) Truck (2) broad feet (c) Knife (3) six or eight tyres (d) High building (4) sharp cutting edge (e) Thrust (5) atm (f) Moment of force (6) N (g) Atmospheric pressure (7) N m
Objective Questions | Q 4.01 | Page 56

SI. unit of moment of force is

• N

• N cm

•  kgfm

•  Nm

Objective Questions | Q 4.02 | Page 56

To obtain a given moment of force for turning a body, the force needed can be decreased by

• applying the force at the pivoted point

• applying the force very close to the pivoted point

• applying the force farthest from the pivoted point

• none of the above

Objective Questions | Q 4.03 | Page 56

The unit of thrust is

• kgf

• kg

• g

• m s-1

Objective Questions | Q 4.04 | Page 56

The unit of pressure is

• N × m

• kgf

• N m-2

• kgf m2

Objective Questions | Q 4.05 | Page 56

The pressure and thrust are related as

• Pressure = Thrust

• Pressure = Thrust x Area

• Pressure = Thrust / Area,

• Pressure = Area / Thrust

Objective Questions | Q 4.06 | Page 56

A body weighing 5 kgf, placed on a surface of area 0.1 m2, exerts a thrust on the surface equal to

• 50 kgf

• 5 kgf

• 50 kgf  m-2

• 5 kgf  m-2

Objective Questions | Q 4.07 | Page 56

The feet of lizards act like

• none of the above

Objective Questions | Q 4.08 | Page 56

Pressure exerted by a liquid is due to it

• weight

• mass

• volume

• area

Objective Questions | Q 4.09 | Page 56

Pressure inside a liquid increases with

• increase in depth

• decrease in depth

• decrease in density

• none of the above

Objective Questions | Q 4.1 | Page 56

The atmospheric pressure at sea level is nearly

• 10 Pa

• 100,000 Pa

• 100 Pa

• 10,000 Pa

Objective Questions | Q 4.11 | Page 56

Nose bleeding may occur at a high altitude because

• the atmospheric pressure decreases

• the oxygen content of atmosphere decreases

• the atmospheric pressure increasess

• there are strong air currents at the high altitude

Short/Long Answer Questions [Pages 56 - 58]

### Selina solutions for Concise Physics Class 8 ICSE Chapter 3 Force and Pressure Short/Long Answer Questions [Pages 56 - 58]

Short/Long Answer Questions | Q 1 | Page 56

Define force. State its S.I. unit.

Short/Long Answer Questions | Q 2 | Page 56

State two effects of a force when applied on a body.

Short/Long Answer Questions | Q 3.1 | Page 56

How does the effect of force differ when it is applied on a rigid body?

Short/Long Answer Questions | Q 3.2 | Page 56

How does the effect of force differ when it is applied on a non-rigid body?

Short/Long Answer Questions | Q 4.1 | Page 56

State the effect of force F in of the following diagram.

Short/Long Answer Questions | Q 4.2 | Page 56

State the effect of force F in  of the following diagram.

Short/Long Answer Questions | Q 5 | Page 56

Define the term moment of force.

Short/Long Answer Questions | Q 6 | Page 56

State the S.I. unit of moment of force.

Short/Long Answer Questions | Q 7 | Page 56

State two factors on which affect moment of force.

Short/Long Answer Questions | Q 8 | Page 57

In Fig. a force F is applied in a direction passing through the pivoted point O of the body. Will the body rotate? Give reason to support your answer.

Short/Long Answer Questions | Q 10 | Page 57

State one way to decrease the moment of a given force about a given axis of rotation.

Short/Long Answer Questions | Q 11 | Page 57

State one way to obtain greater moment of a given force about a given axis of rotation.

Short/Long Answer Questions | Q 12 | Page 57

What do you mean by the clockwise and anti-clockwise moment of force?

Short/Long Answer Questions | Q 13.1 | Page 57

The spanner (or wrench) has a long handle.

Short/Long Answer Questions | Q 13.2 | Page 57

The steering wheel of a vehicle is of large diameter.

Short/Long Answer Questions | Q 13.3 | Page 57

The hand flour grinder is provided with a handle near the rim.

Short/Long Answer Questions | Q 13.4 | Page 57

It is easier to open the door by pushing it at its free end.

Short/Long Answer Questions | Q 13.5 | Page 57

A potter turns his wheel by applying a force through the stick near the rim of wheel.

Short/Long Answer Questions | Q 14 | Page 57

What is thrust?

Short/Long Answer Questions | Q 15 | Page 57

State the unit of thrust

Short/Long Answer Questions | Q 16 | Page 57

On what factors does the effect of thrust on a surface depend?

Short/Long Answer Questions | Q 17 | Page 57

Define the term ‘pressure’ and state its unit.

Short/Long Answer Questions | Q 18 | Page 57

How is the thrust related to pressure?

Short/Long Answer Questions | Q 19 | Page 57

Name two factors on which the pressure on a surface depends.

Short/Long Answer Questions | Q 20 | Page 57

When does a man exert more pressure on the floor: while standing or while walking?

Short/Long Answer Questions | Q 21 | Page 57

Why do camels or elephants have broad feet?

Short/Long Answer Questions | Q 22 | Page 57

A sharp pin works better than a blunt pin. Explain the reason.

Short/Long Answer Questions | Q 23 | Page 57

Why is the bottom part of the foundation of a building made wider?

Short/Long Answer Questions | Q 24 | Page 57

It is easier to cut with a sharp knife than with a blunt one. Explain.

Short/Long Answer Questions | Q 25.1 | Page 57

A gum bottle rests on its base. If it is placed upside down, how does the thrust .

Short/Long Answer Questions | Q 25.2 | Page 57

A gum bottle rests on its base. If it is placed upside down, how does the pressure change?

Short/Long Answer Questions | Q 26.1 | Page 57

Sleepers are used below the rails.

Short/Long Answer Questions | Q 26.2 | Page 57

A tall building has wide foundations.

Short/Long Answer Questions | Q 27 | Page 57

Describe an experiment to show that a liquid exerts pressure at the bottom of the container in which it is kept.

Short/Long Answer Questions | Q 28 | Page 57

Describe a suitable experiment to demonstrate that a liquid exerts pressure sideways also?

Short/Long Answer Questions | Q 29 | Page 57

Describe a simple experiment to show that at a given depth, a liquid exerts same pressure in all directions.

Short/Long Answer Questions | Q 30 | Page 57

State two factors on which the pressure at a point in a liquid depends.

Short/Long Answer Questions | Q 31 | Page 57

Describe an experiment to show that the liquid pressure at a point increases with the increase in height of the liquid column above that point.

Short/Long Answer Questions | Q 32 | Page 57

Which fact about liquid pressure does the diagram in fig. illustrate.

Short/Long Answer Questions | Q 33 | Page 57

Describe an experiment to show that liquid pressure depends on the density of liquid.

Short/Long Answer Questions | Q 34 | Page 57

A dam has broader walls at the bottom than at the top. Give a reason.

Short/Long Answer Questions | Q 35 | Page 57

What do you mean by atmospheric pressure?

Short/Long Answer Questions | Q 36 | Page 57

Write the numerical value of the atmospheric pressure on the earth surface in pascal.

Short/Long Answer Questions | Q 37 | Page 57

We do not feel uneasy even under the enormous atmospheric pressure. Give a reason.

Short/Long Answer Questions | Q 38 | Page 58

Describe a simple experiment to illustrate that air exerts pressure.

Short/Long Answer Questions | Q 39 | Page 58

Describe the crushing tin can experiment. What do you conclude from this experiment?

Short/Long Answer Questions | Q 40.1 | Page 58

Give reason for the following:
A balloon collapses when air is removed from it.

Short/Long Answer Questions | Q 40.2 | Page 58

Give reason for the following:
Water does not run out of a dropper unless its rubber bulb is pressed.

Short/Long Answer Questions | Q 40.3 | Page 58

Give reason for the following :
Two holes are made in a sealed oil tin to take out oil from it.

Short/Long Answer Questions | Q 41 | Page 58

How does the atmospheric pressure change with altitude?

Numericals [Page 58]

### Selina solutions for Concise Physics Class 8 ICSE Chapter 3 Force and Pressure Numericals [Page 58]

Numericals | Q 1 | Page 58

Find the moment of force of 20 N about an axis of rotation at distance 0.5 m from the force.

Numericals | Q 2 | Page 58

The moment of a force of 25 N about a point is 2.5 N m. Find the perpendicular distance of force from that point

Numericals | Q 3 | Page 58

A spanner of length 10 cm is used to open a nut by applying a minimum force of 5.0 N. Calculate the moment of force required.

Numericals | Q 4 | Page 58

A wheel of diameter 2 m can be rotated about an axis passing through its center by a moment of force equal to 2.0 N m. What minimum force must be applied on its rim?

Numericals | Q 5 | Page 58

A normal force of 200 N acts on an area of 0.02 m2. Find the pressure in pascal.

Numericals | Q 6 | Page 58

Find the thrust required to exert a pressure of 50000 pascals on an area of 0.05 m2 ?

Numericals | Q 7 | Page 58

Find the area of a body which experiences a pressure of 50000 Pa by a thrust of 100 N?

Numericals | Q 8 | Page 58

Calculate the pressure in pascal exerted by a force of 300 N acting normally on an area of 30 cm2.

Numericals | Q 9 | Page 58

How much thrust will be required to exert a pressure of 20,000 Pa on an area of 1 cm2.

Numericals | Q 10 | Page 58

The base of a container measures 15 cm × 20 cm. It is placed on a table top. If the weight of the container is 60 N, what is the pressure exerted by the container on the table top?

Numericals | Q 11 | Page 58

Calculate the pressure exerted on a surface of 0.5 m2 by a thrust of 100 kgf.

Numericals | Q 12 | Page 58

A boy weighing 60 kgf stands on platform of dimensions 2.5 cm x 0.5 cm. What pressure in pascal does he exert?

Numericals | Q 13 | Page 58

Figure shows a brick of weight 2 kgf and dimensions 20 cm x 10 cm × 5 cm placed in three different positions on the ground. Find the pressure exerted by the brick in each case.

## Selina solutions for Concise Physics Class 8 ICSE chapter 3 - Force and Pressure

Selina solutions for Concise Physics Class 8 ICSE chapter 3 (Force and Pressure) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CISCE Concise Physics Class 8 ICSE solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Concise Physics Class 8 ICSE chapter 3 Force and Pressure are Turning Effect of a Force, Atmospheric Pressure, Moment of Force Or Torque, The Effect of Thrust, Factors Affecting Pressure, Factors Affecting Liquid Pressure, Consequences of Liquid Pressure, Standard Value of Atmospheric Pressure, Force, Thrust and Pressure, Liquid Pressure, Application of Atmospheric Pressure.

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