#### Chapters

Chapter 2: Work, Energy and Power

Chapter 3: Machines

Chapter 4: Refraction of Light at Plane Surfaces

Chapter 5: Refraction through a Lens

Chapter 6: Spectrum

Chapter 7: Sound

Chapter 8: Current Electricity

Chapter 9: Electrical Power and Household Circuits

Chapter 10: Electro-Magnetism

Chapter 11: Calorimetry

Chapter 12: Radioactivity

## Chapter 1: Force

#### Exercise -1 (A), Exercise - 1 (A), Exercise -1(A), Exercise - 1(A) [Pages 9 - 10]

### Selina solutions for Concise Physics Class 10 ICSE Chapter 1 Force Exercise -1 (A), Exercise - 1 (A), Exercise -1(A), Exercise - 1(A) [Pages 9 - 10]

State the condition when on applying a force, the body has:

the translational motion

State the condition when on applying a force, the body has:

the rotational motion.

Define moment of force and state its S.I unit.

State whether the moment of force is a scalar or vector quantity?

State two factors affecting the turning effect of a force.

When does a body rotate? State one way to change the direction of rotation of a body. Given a suitable example to explain your answer.

Write the expression for the moment of force about a given axis.

What do you understand by the clockwise and anticlockwise moment of force? When is it taken positive?

State one way to reduce the movement of given force about a given axis of rotation.

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

Why is it easier to open a door by applying the force at the free end of it?

The stone of hand flour grinder is provided with a handle near its rim. Give reason.

It is easier to turn the steering wheel of a large diameter than that of a small diameter. Given reason.

A spanner (or wrench) has a long handle. Why?

A jack screw is provided with a long arm. Explain why?

A, B and C are the three forces each of magnitude 4 n acting in the plane of the paper as shown in Figure. The point O lies in the same plane.

1) Which force has the least moment about O? Give a reason.

2) which force has the greatest moment about O? Give a reason.

3) Name the forces producing (a) Clockwise (b) anticlockwise moments.

4) what is the resultant torque about the point O?

The adjacent diagram shows a heavy roller, with its axle at O. which its axle at O. which is to be raised on a pavement XY by applying a minimum possible force. show by an arrow on the diagram the point of application and the direction in which the force should be applied.

A body is acted upon by two force of magnitude F but in opposite direction. State the effect of the force if

both forces act at the same point of the body.

A body is acted upon by two force of magnitude F, but in opposite directions. State the effect of the force if

the two forces act at two different points of the body at a separation r.

Draw a neat labelled diagram to show the direction of two forces acting on a body to produce rotation in it. Also, mark the point about which rotation takes place by the letter O.

What do you understand by the term couple?

State the couple effect. Give two example of couple action in our daily life.

Define moment of couple. Write its S.I unit

Prove that Moment of couple = Force x couple arm.

What do you mean by an equilibrium of a body?

State the condition when a body is in static equilibrium. Give one example of static equilibrium.

State the condition when a body is in dynamic equilibrium. Give one example of dynamic equilibrium.

State two condition for a body acted upon by several forces to be in equilibrium.

State the principle of moments. Give one device as an application of it

Describe a simple experiment to verify the principle of moments, if you are supplied with a metre rule, a fulcrum and two springs with slotted weights.

Complete the following sentence :

The S.I. unit of moment of force is _________.

Complete the following sentence :

In equilibrium algebraic sum of moments of all forces about the point of rotation is ______________.

Complete the following sentence :

In a beam balance when the beam is balanced in a horizontal position, it is in ____________equilibrium.

Complete the following sentence :

The moon revolving around the earth is in ____________ equilibrium.

#### Exercise - 1 (A) [Pages 10 - 11]

### Selina solutions for Concise Physics Class 10 ICSE Chapter 1 Force Exercise - 1 (A) [Pages 10 - 11]

Multiple choice Type:

The moment of a force about axis depends:

Only on the magnitude of force

Only on the perpendicular distance of force from the axis

Neither on the force nor on the perpendicular distance of force from the axis

Both on the force and its perpendicular distance from the axis.

Multiple choice Type:

A body is acted upon by two unequal forces in opposite directions, but not in the same line. The effect is that:

The body will have only the rotational motion

The body will have only the translational motion

The body will have neither the rotational motion nor the translational motion

The body will have rotational as well as translational motion.

#### Exercise - 1 (A) [Pages 11 - 12]

### Selina solutions for Concise Physics Class 10 ICSE Chapter 1 Force Exercise - 1 (A) [Pages 11 - 12]

The moment of a force of 10 N about a fixed point O is 5 N m. Calculate the distance of the point O from the line of action of the force.

A nut is opened by a wrench of length 10 cm. if the least force required is 5.0 N. find the moment of force needed to turn the nut.

A wheel of diameter2 m is shown in the figure with the axle at O. A force F = 2 N is applied at B in the direction shown in the figure. Calculate the moment of force about Centre O and point A.

The diagram in the figure shows two forces F_{1} = 5 N and F_{2} = 3N acting at point A and B of a rod pivoted at a point O, such that OA = 2m and OB = 4m

Calculate:

1) Moment of force F_{1} about O

2) Moment of force F_{2} about O

3) Total moment of the two forces about O.

Two forces each of magnitude 10 N act vertically upwards and downwards respectively at the two ends of a uniform road of length 4m which is pivoted at its midpoint as shown in the figure. Determine the magnitude of the resultant moment of forces about the pivot O.

The figure shows two forces each of magnitude 10 N acting at the point A and B at a separation of 50 cm, in opposite directions. Calculate the resultant moment of two forces about the point A, B and O, situated exactly at the middle of the two forces.

A steering wheel of diameter 0.5 m is rotated anticlockwise by applying two forces each of magnitude 5 N. Draw a diagram to show the application of forces and calculate the moment of couple applied.

A uniform metre rule is pivoted at its mid-point. A weight of 50 gf is suspended at one end of it. where should a weight of 100 gf be suspended to keep the rule horizontal?

A uniform metre rule balance horizontally on a knife-edge placed at the 58 cm mark when a weight of 20 gf is suspended from one end.

Draw a diagram of the arrangement.

A uniform metre rule balances horizontally on a knife edge placed at the 58 cm mark when a weight of 20gf is suspended from one end.

What is the weight of the rule?

The diagram below Shows a uniform bar supported at the middle point O. A weight of 40 gf is placed at a distance of 40 cm to the left of the point O. How can you balance the bar with a weight of 80 gf?

The figure shows a uniform metre rule placed on a function at its mid-point O and having a weight 40 gf at the 10 cm mark and a weight of 20 gf at the 9.0 cm mark.

Is the metre rule in equilibrium? If not how will the rule turn?

Figure shows a uniform metre rule placed on a fulcrum at its mid-point O and having a weight 40gf at the 10 cm mark and a weight of 20gf at the 90 cm mark.

How can the rule be brought in equilibrium by using an additional weight of 40 gf ?

When a boy weighing 20 kgf sits at one end of a 4 m long see saw, it gets depressed at this end. How can it be brought to the horizontal position by a man weighing 40 kgf

A physical balance has its arms of length 60 cm and 40 cm. What weight kept on pan of the longer arm will balance an object of weight 100 gf kept on other pan?

The diagram in the figure shows a uniform metre rule weighing 100 gf, pivoted as its centre O. two weight 150 gf and 250 gf hang from the point A and B respectively of the metre rule such that OA = 40 cm and OB = 20 cm . Calculate

the total anticlockwise moment about o.

The diagram shows a uniform metre rule weighing 100gf, pivoted at its centre O. Two weights 150gf and 250gf hang from the point A and B respectively of the metre rule such that OA = 40 cm and OB = 20 cm. Calculate :

the total clockwise moment about O

The diagram shows a uniform metre rule weighing 100gf, pivoted at its centre O. Two weights 150gf and 250gf hang from the point A and B respectively of the metre rule such that OA = 40 cm and OB = 20 cm. Calculate :

the difference of anticlockwise and clockwise moment

The diagram shows a uniform metre rule weighing 100gf, pivoted at its centre O. Two weights 150gf and 250gf hang from the point A and B respectively of the metre rule such that OA = 40 cm and OB = 20 cm. Calculate :

the distance from O where a 100gf weight should be placed to balance the metre rule.

A uniform metre rule of weight 10gf is pivoted at its 0 mark.

What moment of force depresses the rule?

A uniform metre rule of weight 10gf is pivoted at its 0 mark.

How can it be made horizontal by applying a least force ?

A uniform half metre rule can be balanced at the 29.0 cm mark when a mass 20g is hung from its one end.

1) Draw a diagram of the arrangement.

2) Find the mass of the half metre rule.

A uniform metre rule of mass 100 g is balanced on the fulcrum at mark 10 cm by suspending an unknown mass M at the mark 20 cm.

Find the value of M.

A uniform metre rule of mass 100g is balanced on a fulcrum at mark 40cm by suspending an unknown mass m at the mark 20cm.

To which side the rule will tilt if the mass m is moved to the mark 10cm ?

A uniform metre rule of mass 100g is balanced on a fulcrum at mark 40cm by suspending an unknown mass m at the mark 20cm.

What is the resultant moment now ?

A uniform metre rule of mass 100g is balanced on a fulcrum at mark 40cm by suspending an unknown mass m at the mark 20cm.

How can it be balanced by another mass 50 g ?

In following figure , a uniform bar of length l m is supported at its ends and loaded by a weight W kgf at its middle. In equilibrium, find the reactions R_{1} and R_{2} at the ends.

`["Hint" : "In equilibrium" "R"_1 + "R"_2 = "W" "and" "R"_1 xx 1/2 = "R"_2 xx 1/2]`

#### Exercise - 1 (B) [Pages 14 - 15]

### Selina solutions for Concise Physics Class 10 ICSE Chapter 1 Force Exercise - 1 (B) [Pages 14 - 15]

Define the term centre of gravity of a body.

Can the centre of gravity be situated outside the material of the body? Give an example

On what factor does the position of the centre of gravity of a body depend? Explain your answer with an example.

What is the position of the centre of gravity of a rectangular lamina?

What is the position of the centre of gravity of a cylinder?

At which point is the centre of gravity situated in a triangular lamina.

At which point is the centre of gravity situated in a circular lamina?

Where is the centre of gravity of a uniform ring situated?

A square cardboard is suspended by passing a pin through a narrow hole at its one corner. Draw a diagram to show its rest position. In the diagram, mark the point of suspension by the letter S and the centre of gravity by the letter G.

Explain how you will determine the position of the centre of gravity experimentally for a triangular lamina (or a triangular piece of cardboard)

**State True or False**

The position of the centre of gravity of a body remains unchanged even when the body is deformed.

True

False

State True or False

Centre of gravity of a freely suspended body always lies vertically below the point of suspension.

A uniform flat circular rim is balanced on a sharp vertical nai by supporting it at point A, as shown in the figure. Mark the position of the centre of gravity of the rim in the diagram by the letter G.

The figure shows three pieces of cardboard of uniform thickness cut into three different shapes. On each diagram draw two lines to indicate the position of the centre of gravity G.

#### Exercise - 1 (B) [Page 15]

### Selina solutions for Concise Physics Class 10 ICSE Chapter 1 Force Exercise - 1 (B) [Page 15]

The centre of gravity of a uniform ball is

a) at its geometrical centre

b) at its bottom

c) at its topmost point

d) at any point on its surface

at its geometrical centre

at its bottom

at its topmost point

at any point on its surface

The centre of gravity of a hollow cone of height h is at distance x from its vertex where the value of x is:

`"h"/3`

`"h"/4`

`"2h"/3`

`"3h"/4`

#### Exercise - 1 (C) [Page 18]

### Selina solutions for Concise Physics Class 10 ICSE Chapter 1 Force Exercise - 1 (C) [Page 18]

Explain the meaning of uniform circular motion. Give one example of such motion.

Draw a neat labelled diagram for a particle moving in a circular path with a constant speed. In you diagram show the direction of velocity at any instant.

Is it possible to have an accelerated motion with a constant speed? Name such type of motion.

Give an example of motion in which speed remains uniform, but the velocity changes.

A uniform circular motion is an accelerated motion explain it. State whether the acceleration is uniform or variable? Name the force responsible to cause this acceleration. What is the direction of force at any instant? Draw diagram in support of your answer.

Differentiate between Uniform linear motion and Uniform circular motion.

Name the force required for circular motion. State its direction.

What is a centripetal force?

Explain the motion of a planet around the sun in a circular path.

With reference to the direction of action, how does a centripetal force differ from centrifugal force?

Is centrifugal force the force of rection of centripetal force?

Compare the magnitudes of centripetal and centrifugal force.

Is centrifugal force a real force?

A small pebble is placed near the periphery of a circular disc which is rotating about an axis passing through it centre.

(a) What will be your observation when you are standing outside the disc? Explain it

(b) What will be your observation when you are standing at the centre of the disc. Explain it

A piece of stone tied at the end of a thread is whirled in a horizontal circle. Name the force which provides the centripetal force.

- Is the velocity of stone uniform or variable?
- Is the acceleration of stone uniform or variable?
- What is the direction of acceleration of stone at any instant?
- What force does provide the centripetal force required for circular motion?
- Name the force and its direction which acts on the hand.

State two differences between the centripetal and centrifugal force.

State True or False

The earth moves around the sun with a uniform.

True

False

State True or False

The motion of the moon around the earth in a circular path is an accelerated motion.

True

False

State True or False:

A uniform linear motion is unaccelerated , while a uniform circular motion is an accelerated motion.

True

False

State True or False

In a uniform circular motion, the speed continuously changes because of the direction of motion changes.

True

False

State whether the following statement are true or false by writing T/F against them.

A Boy experiences a centrifugal force on his hand when he rotates a piece of stone tied at one end of a string, holding the other end in the hand.

True

False

#### Exercise - 1 (C) [Pages 0 - 18]

### Selina solutions for Concise Physics Class 10 ICSE Chapter 1 Force Exercise - 1 (C) [Pages 0 - 18]

Which of the following quantity remains constant in uniform circular motion:

Velocity

Speed

Acceleration

Both velocity and speed

The centrifugal force is:

a real force

the force of reaction of centripetal force

a fictitious force

directed towards the centre of circular path

## Chapter 1: Force

## Selina solutions for Concise Physics Class 10 ICSE chapter 1 - Force

Selina solutions for Concise Physics Class 10 ICSE chapter 1 (Force) 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 10 ICSE solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Concise Physics Class 10 ICSE chapter 1 Force are Turning Forces Concept, Moment of a Force, Forces in Equilibrium, Centre of Gravity, Force - Uniform Circular Motion, Concept of Force, Elementary Introduction of Translational and Rotational Motions, Turning Effect of Force (Moment of Force).

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