#### 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

#### Selina Selina ICSE Concise Physics Class 10

## Chapter 1: Force

#### Chapter 1: Force solutions [Page 0]

What are contact forces? Give two Example

What are non-contact forces? Give two example

Classify the following amongst contact and non-contact forces.

Frictional force

Classify the following amongst contact and non-contact forces.

normal reaction force,

Classify the following amongst contact and non-contact force.

force of tension in a string

Classify the following amongst contact and non-contact forces.

gravitation force

Classify the following amongst contact and non-contact forces.

electrostatic force

Classify the following amongst contact and non-contact forces.

magnetic force

Give one example in the case where the force is of contact.

Give one example in the case where Force is at a distance.

A ball is hanging by a thread from the ceiling of the roof. Draw a neat labelled diagram showing the forces acting on the ball and the string

A spring is compressed against a rigid wall. Draw a neat and labelled diagram showing the forces acting on the spring.

State one factor on which the magnitude of a non-contact force depends. How does it depend on the factor stated by you?.

The separation between two masses is reduced to half. How is the magnitude of the gravitational force between them affected?

Define the term Force?

State the effects of a force applied on a non-rigid and a rigid body. How does the effect of the force differ in the two cases?

Give one example in the given cases:

A force stops a moving body

Give one example in the given cases:-

A force moves a stationary body

Give one example in the given cases:-

A force changes the size of a body

Give one example in the given cases:-

A force changes the shape of a body

Give one example in the given cases:-

A force changes the shape of a body

State Newton's first law of motion. Why is it called the law of inertia?

Define the term linear momentum. State its S.I unit.

Write an expression for the change in momentum of a body of mass m moving with velocity v if v << c.

State the condition when the change in the momentum of a body depends only on the change in its velocity.

How is force related to the momentum of a body?

State Newton's Second law of motion. Under what conditon does it take the form F = ma?

Complete the following sentence:

Mass X change in velocity = ............x time interval.

Complete the following sentence:

The mass of a body remains constant till the velocity of the body is ..........

Prove the force = mass x acceleration. State the condition when it holds.

Name of S.I. unit of momentum.

Name of S.I. unit of the rate of change in momentum.

State the relationship between force, mass and acceleration. Draw graphs showing the relationship between Acceleration and force for a constant mass.

State the relationship between force, mass and acceleration. Draw graphs showing the relationship between Acceleration and mass for a constant force.

A rocket is moving at a constant speed in space by burning its fuel and ejecting out the burnt gases through a nozzle. Answer the following

1) Is there any change in the momentum of the rocket? if yes, what causes the change in momentum?

2) Is there any force acting on the rocket? if yes, how much?

State Newton's third law of motion.

Name and define the S.I and C.G.S unit of force. How are they related?

Define Newton (the S.I unit of force)

Define 1 kgf how is it related to Newton?

Explain what is understood by the following statement 1 kilogram-force (kgf) - 9.8 newton

How can you feel a force of 1 N?

Complete the following:

Force = mass x ............

Complete the following

1 N = ..........dyne.

Complete the following:

1 N = ............kgf (approx)

Complete the following

Newton is the unit of .................

#### Chapter 1: Force solutions [Page 0]

Which of the following is not the force at a distance:

(a) electrostatic force

(b) gravitational force

(c) frictional force.

(d) magnetic force.

Newton's second law of motion applicable in all condition is:

(a) `F = (Δp)/(Δt)`

(b) F = ma

(c) `F = M (Δv)/(Δt)`

(d) all three

#### Chapter 1: Force solutions [Page 0]

A body of mass 1 kg is thrown vertically up with an initial speed of 5 m s^{-1}. What is the magnitude and direction of force due to gravity acting on the body when it is at its highest point? Take G = 9.8 n kg^{-1}

A body of mass 1.5 kg is dropped from a height of 12 m. What is the force acting on it during its fall? (g = 9.8 ms^{-2})

Two balls of masses in ratio 1 : 2 are dropped from the same height find

a) the ratio between their velocities when they strike the ground and

b) the ration if the forces acting on them during motion.

A body X of mass 5 kg is moving with velocity 20 m s^{-2} while another body Y of mass 20 kg is moving with velocity 5 m S^{-1}. Compare the momentum of the two bodies.

Calculate the acceleration produced in a body of mass 50 g when acted upon by a force of 20 N.

A car of mass 600 kg is moving with a speed of 10 ms^{-1} while a scooter of mass 80 kg us moving with a speed of 50 ms^{-1}. Compare their momentum.

A car of mass 600 kg is moving with a speed of 10 m^{-1 }while a scooter of mass 80 kg is moving with speed of 50 m s^{-1}. which vehicle will require more force to stop it in the (1) same interval of time (2) same distance

How much acceleration will be produced in a body of mass 10 kg acted upon by a force of 2 kgf?(g = 9.8 ms^{-2})

Two bodies have masses in the ratio 3 : 4 when a force is applied on the first body. it moves with an acceleration of 6 ms^{-2} . How much acceleration will the same force produce in the other body?

A cricket ball of mass 100 g strikes the hand of a player with a velocity of 20 ms^{-1} and is brought to rest in 0.01 s calculate

1) the force applied by the hand of the player.

2) the acceleration of the ball

A lead bullet of mass 20g, travelling with a velocity of 350 ms^{-1}, comes to rest after penetrating 40 cm in a still target. Find:

1) the resistive force offered by the target and

2) the retardation caused by it

A body of mass 50g is moving with the velocity of 10 ms^{-1}. It is brought to rest by a resistive force of 10 N Find.

1) the retardation and

2) the distance that the body will travel after the resistive force is applied.

A uniform car of mass 500g travels with a uniform velocity of 25 ms^{-1} for 5 s. The brakes are then applied and the car is uniformly retarded and comes to rest in further 10 s calculate

1) the retardation

2) the distance which the car travels after the brakes are applied

3) The force exerted by the brakes.

A truck of mass `5 xx 10^3` kg starting from rest travels a distance of 0.5 km in 10 s when a force is applied on its calculate:

1) the acceleration acquired by the truck and

2) the force applied

A force od 10 kgf is applied on a body of mass 100 g initially at rest for 0.1 s calculate:

a) the momentum acquired by the body

b) the distance travelled by the body in 0.1s. Take g = 10 N kg^{-1}

#### Chapter 1: Force solutions [Page 0]

State the condition when a force produces translational motion.

State the condition when a force produces rotational motion in a body.

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

Is moment of force a scalar or a vector?

State two factor on which moment of force about a point depends.

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 calculating the moment of force about a given an axis.

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

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

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, 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 forces each of magnitude F but in opposite direction. State the effect of the forces if

a) both forces act at the same point of the body.

b) the two forces act at two different point g 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.

#### Chapter 1: Force solutions [Page 0]

Multiple choice Type:

The moment of a force about axis depends:

a) only on the magnitude of the force

b) Only on the perpendicular distance of force from the axis.

c) neither on the force nor on the perpendicular distance of from the axis.

d) 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:

a) the body will have only the rotational motion

b) the body will have only the translational motion

c) the body will have neither the rotational motion nor the translation motion.

d) the body will have rotational as well as translational motion

#### Chapter 1: Force solutions [Page 0]

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.

1) Draw a diagram of the arrangement

2) 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.

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

2) 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 metre rule as shown

1) the total anticlockwise moment about o.

2) the total clockwise moment about O.

3) the difference of anticlockwise and clockwise moments,

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

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

1) What moment of force depresses the rule?

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

A uniform metre scale can be balanced at the 70.0 cm mark when a mark when a mass 0.05 kg is hung from the 94.0 cm mark

1) draw a diagram of the arrangement

2) Find the mass of the metre scale

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.

1) Find the value of M.

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

3) what is the resultant moment now?

4) How can it be balanced by another mass of 50 g?

#### Chapter 1: Force solutions [Page 0]

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

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.

#### Chapter 1: Force solutions [Page 0]

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

#### Chapter 1: Force solutions [Page 0]

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.

Differentiate between Uniform linear motion and Uniform circular motion.

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

What is a centripetal force?

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.

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?

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

State True or False

The earth moves around the sun with a uniform.

State True or False

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

State True or False:

A uniform linear motion is an accelerated motion.

State True or False

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

#### Chapter 1: Force solutions [Page 0]

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

a) Velocity

b) speed

c) acceleration

d) both velocity and speed

## Chapter 1: Force

#### Selina Selina ICSE Concise Physics Class 10

#### Textbook solutions for Class 10

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

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

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Concepts covered in Class 10 Physics 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.

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