9th Class Physics Chapter 3 Short Questions with Answers Solved

Question: 1

Define Momentum.

Answer: 1

1-104

Momentum of a body is the quantity of motion it possesses due to its mass and velocity. Formula ; P = m x v Unit: Kgms-1 or Ns.

Question: 2

Define Tension in a string:

Answer: 2

2-104

The force acting along a string is called tension. Its unit is newton . It is represented by 'T'

Question: 3

What is the law of inertia?

Answer: 3

3-104

Since Newton's first law of motion deals with the inertial property of matter, there fore ,Newton's first law of motion is also known as law of inertia stated as. A body continues its state of rest or of uniform motion in a straight line provided no net force asct on it.

Question: 4

Define Circular motion:

Answer: 4

4-104

If a body move in circular path its motion is known as circular motion.

Question: 5

Difference between sliding friction and Rolling friction.

Answer: 5

5-104

Sliding friction: In sliding friction the surface of a body moves by sliding against the surface of another body.

Question: 6

Why is it dangerous to travel on the roof of a bus.

Answer: 6

6-104

The friction or drag force due to air acting on upper part of the body of a person standing on roof of a running bus, tries to turn over which is dangerous while the lower part of the body is rest with respect to the roof of the bus.

Question: 7

Define friction.

Answer: 7

7-104

The force that opposes the motion of moving object is called friction.

Question: 8

Define Banking of roads.

Answer: 8

8-104

Banking of a road means that the outer edge of a road is raised. Outer edge of the curved road is elevated to prevent skidding.

Question: 9

Define Cream separator:

Answer: 9

9-104

Most modern plants use a separator to control the fat contents of various product. A seperator is a high-speed spinner. It acts on the same principle of centrifuge machines.

Question: 10

Difference between Mass or Weight.

Answer: 10

10-104

Mass: i. Mass of a body is the quantity of matte possessed by the body 2. It is a scalar quantity 3. It is measured by using a common balance. 4. It remains same every where. 5. The SI unit of mass is kilogram 6. It is base quantity.

Question: 11

Define net force.

Answer: 11

11-104

Net force is the resultant of all forces acting on a body.

Question: 12

Define Braking force.

Answer: 12

12-104

When we drive a car on a road and we suddenly apply a brake on a wheel of our car. it will stop is called braking.

Question: 13

State first law of motion.

Answer: 13

13-104

A body continues its state of rest or of uniform motion in a straight line provided no net force acts on it. It is also called law of inertia.

Question: 14

Write two method of reducing friction.

Answer: 14

14-104

Making the sliding surfaces smooth By converting sliding friction into rolling friction.

Question: 15

A horse pushes the cart. If the action and reaction are equal and opposites,then how does the cart move?

Answer: 15

15-104

When a horse pushes the ground the ground reacts and exerts a force on the horse in the forward direction. The force is able to overcomefriction force of the cart and it moves.

Question: 16

What is action in above example.

Answer: 16

16-104

Action is weight of book acting downward on the table.

Question: 17

Define limiting frictions.

Answer: 17

17-104

The maximum value of static friction is known the force of limiting friction Fs=μmg

Question: 18

Define Coefficient offriction, cream separator, banking of road?

Answer: 18

18-104

A coefficient of friction is a value that shows the relationship between the force of friction between two objects and the normal reaction between the objects are involved.

Question: 19

What is meant by centrifugal force.

Answer: 19

19-104

The reaction of centripetal force is called centrifugal force. Fc=mv2/r

Question: 20

What is inertia

Answer: 20

20-104

Inertia of a body is its property due to which it resists any change in its state of rest or motion

Question: 21

A force of 20N moves a body with an acceleration of 2ms-²What is tits mass?

Answer: 21

21-104

F= 20N

a= 2ms-²

m=?

F=maor m= F/a

m=20/2=10kg

Mass is 10 kg

Question: 22

Why is it easy to roll a cylindrical eraser on a paper sheet than to slide it?

Answer: 22

22-104

Because the sliding friction is greater than rolling friction. So rolling is easy than sliding .

Question: 23

When a gun is fired, it recoils, Why?

Answer: 23

23-104

Because of Newton third law of motion. When a bullet is fired from a gun the force sending the bullet is equal to the force sending the gun backward.

Question: 24

Define unit of force.

Answer: 24

24-104

Unit of force is Newton. 1 N is a force that produced an acceleration of 1 ms-2 in a body of mass of 1 kg.

Question: 25

Describe two situations in which force of friction is needed

Answer: 25

25-104

We cannot rite without friction between paper and the pencil

We cannot walk without friction Friction enables us to walk on the ground.

Question: 26

What are the factor on which friction depends?

Answer: 26

26-104

Nature of two surfaces in contact pressing force between the surfaces in contact.

Question: 27

Difference between Mass and Weight?

Answer: 27

27-104

Mass

1- Mass of a body is the quantity of matter possessed by the body

2- It is a scalar quantity

Question: 28

What is meant by rolling friction?

Answer: 28

28-104

The force of friction between a rolling body and a surface over which it rolls is called rolling friction.

Question: 29

What is an Atwood machine

Answer: 29

29-104

Atwood machine is an arrangement of two objects of unequal masses. Both the objects are attached to the ends of a string. The string passes over a frictionless pulley. The arrangement is sometimes used to find the acceleration due to gravity.

Question: 30

Define sliding friction and rolling friction?

Answer: 30

30-104

Sliding friction is also known as kinetic friction or moving friction and is defiend as the force that is required to keep a surface sliding along another surface.

Rolling friction

Resistance to motion by bodies that are in rolling contact

Question: 31

What is isolated system.

Answer: 31

31-104

An isolated system is a group of interacting bodies on which no external force is acting.

Question: 32

What do you mean by skidding ?

Answer: 32

32-104

Motion of wheel without rotation is called skidding.

Question: 33

Why is the law of conservation of momentum important

Answer: 33

33-104

Rockets and jet engines also work on the same principle. With the help of law of conservation of momentum it is possible to calculate force, velocity, acceleration of a body. Many elementary particles are discovered by using law of conservation of momentum.

Question: 34

What is meant by sliding friction.

Answer: 34

34-104

When two bodies slid over one another, the force of friction between them is known as sliding friction.

Question: 35

Define friction and write equation.

Answer: 35

35-104

The force that opposes the motion of moving objects is called friction. Fs=μmg

Question: 36

Difference between kinematics and Dynamic?

Answer: 36

36-104

Kinematics is the study of motion and position, or the geometry of an event.

Question: 37

What is the difference between action and reaction

Answer: 37

37-104

Action: The force exerted by external agency on a system is called action.

Question: 38

Define Newton's second law.

Answer: 38

38-104

When a force act on body it produce acceleration in the direction of force. The magnitude of acceleration is directly proportional to applied net force. F = ma

Question: 39

Define Tension in a string, Braking force Momentum?

Answer: 39

39-104

TheTension force is the force that is transmitted through a string, rope, cable or wire when itpulled tight by the force acting from opposite ends

Question: 40

What is action in above example

Answer: 40

40-104

Action is weight of book acting downward on the table.

Question: 41

State newton's third law of motion.

Answer: 41

41-104

To every action there is alwasys an equal but opposite reaction e.g. a launching of rocket.

Question: 42

In which case it is easy for the tireto roll over? Rough ground

Answer: 42

42-104

Rough ground:

In case of rough ground, it is difficult for the type the roll over because rough surface offers more friction.

Smooth ground:

Incase of smooth ground it is easier for the type to roll over because smooth surface offer less friction.

Question: 43

What is meant by dynamics?

Answer: 43

43-104

The branch of mechanics that deals with study of motion of an object and the cause of its motion is called dynamics.

Question: 44

A horse pushes the cart It the action and reaction are equal and opposite then how does the cart move.

Answer: 44

44-104

The horse apply action on the road by his feet the reaction is given b y the road on the horse due to which horse moves. The cart which is tied with the horse will also move.

Question: 45

State Newton third law of Motion?

Answer: 45

45-104

To every action there is always an equal but opposite reaction

Question: 46

Why the spinner of a washing machine is made to spin at a very high speed?

Answer: 46

46-104

As the spin of water, water is pulled from the wet clothes through the small holes in the inner-tube into the outer-tube due to centrifugal force. This helps to reduce dry time by leaving your clothes only slightly damp, rather than sopping wet after washing

Question: 47

Differentiate between sliding friction and rolling friction.

Answer: 47

47-104

Sliding friction: The frictional force produced between a body and surface when it rotates on the surface is called sliding friction.

Question: 48

Find the acceleration produced by a force of 100N in a mass of 50kg

Answer: 48

48-104

Mass=-m=50kg

Force=f=100N

To Find

Acceleration a=?

Formula: F=ma

a=f/m

puting the value we get

a100N/50kg=100kgm/50kg

a=2ms

Question: 49

What will be the tension in a ropethat is pull from its ends by two opposite forces 100N?

Answer: 49

49-104

The tension in a rope that is pulledfrom its ends by two opposite forces 100N each will be 100 N

Question: 50

What is the law of inertia

Answer: 50

50-104

Since Newton's first law of motion deals with the inertial property of matter therefore Newton first law of motion is also known as law of inertia stated as

A body continues its state of rest or of uniform motion in a straight line provided on net force act on it.

Question: 51

What would happen if all friction suddenly disappears?

Answer: 51

51-104

If all friction suddenly disappears, everyone dies because you can'twalk or do anything.

Question: 52

Define inertia. Describe two of inertia.

Answer: 52

52-104

Inertia of a body is its property due to which it resists any change in its state of rest on motion.

Example 1:

Take a glass cover it with a piece of cardboard. Now kick the card horizontally with a Jerk of your finger. The coin does not move with the cardbeardwith the inertia and falls in to the glass

Example 2:

Cut a strip of paper, place it on the table. Stack a few coins at its on end. Stack a few coins at its an end pull out the paperstrip under the coins with a jerk we will succeed in pulling out the paper strip under the stacked coinwithout letting them to fall.

Question: 53

Stretch out your palm and hold a book on it. How much force you neend to prevent the book from falling

Answer: 53

53-104

We need a force equal to the weight of book to prevent it from falling

Question: 54

What is the advantage of bankingof road?

Answer: 54

54-104

When a road is banked in a tight turn a lot of the normal radiationbalances the centrifugal force so that we are not entirely dependent on friction which also force torque and can overturn the vehicle in tight turns.

Question: 55

Why is it dangerous o travel on the roof of a bus

Answer: 55

55-104

The friction or drag force due to air acting on upper part of the body of a person standing on roof of a running bus tries to turn over which is dangerous while the lower part of the body is at rest with respect to the roof of the bus

Question: 56

Action and reaction are always equal and opposite. Then how does a body moves?

Answer: 56

56-104

Action and reaction are equal in magnitude but opposite in direction. Action and reaction do not act on the same body. Action is applied on the body due to which an equal and opposite reaction is acting on another body. Both of these do notneutralize each other due to which the body will move.

Question: 57

Which shoes is better for jugging

Answer: 57

57-104

The shoes whose grip is strong on ground is better for jugging these shoes provide more friction for strong grip on road and prevent to falling

Question: 58

why do passengers fall outward of the bus when a bus takes a sharp turn

Answer: 58

58-104

When bus takes a sharp turn the passengers fall in the outward direction it is due to the inertia that they want to continue their motion in a straight line and thus fall outward.

Question: 59

Why is it dangerous to travel at the roof of a bus

Answer: 59

59-104

Because the friction force due air actingon the upper of body of the person who is travelling on the roof of the bus try to turn over which is dangerous for passenger while the lower portion remain at rest w.r.t the roof of the bus

Question: 60

What is force

Answer: 60

60-104

Force is a agency which moves or tends to move stop or tends to stop the motion of a body The force can also change the direction of motion of a

Question: 61

Action and reaction are always equal and opposite. Then how does a body moves?

Answer: 61

61-104

Action and reaction are equal in magnitude butopposite in direction.

Action and reaction do not act on the same body. Action is applied on the body due to which an equal and opposite reaction is acting on another body.Both of these do not neutralize each other due to which the body will move

Question: 62

Why rolling friction is less than sliding friction

Answer: 62

62-104

Rolling friction is the force of friction between a rolling body and a surface over which it rolls. So in rolling friction there is no interlocking in cold welds but in sliding friction there is interlocking The roling objects just roll over each other hence area of contact is less than that of sliding. Thus rolling friction is less than sliding friction.

Question: 63

State Newton Second Law of motion?

Answer: 63

63-104

When a net force `F' acts on a body it produces an accelerationin the body direction of force and the magnitude of acceleration id directly proportional to the force and is inversely proportional to the mass of the body.

Question: 64

Define newton, Circular motion?

Answer: 64

64-104

Remember that Newton's Second law of Motion States that force is equal to mass times acceleration, and uniform circular motion refers to perfectly circular motion around a center point.

Question: 65

A force of 20n moves a body with an acceleration of 2

Answer: 65

65-104

Given data Force=F=20N

acceleration =a=2ms

m=?

We know that f=ma

Question: 66

Define centripetal force and give formula

Answer: 66

66-104

Centripetal force is a force that keeps a body to move in a circle.

Question: 67

What do you know about following

Answer: 67

67-104

Tension in a string, Banking of roads, Braking force, Cream separator.

Question: 68

How can you relate a force with the change of momentum of a body

Answer: 68

68-104

When a force acts on a body it produces acceleration in the body and it will be equal to the rate of change of momentum of the body.

Question: 69

What would happen if all friction disappears

Answer: 69

69-104

If all friction disappears, there will be no existence of life.

Question: 70

When a gun is fired, it recoils.

Answer: 70

70-104

Total momentum o the gun and the bullet is zero before the firing. When gun fired, bullet moves in forward direction and gun recoils so theat total momentum after firing also becomes zero according to law of conservation of momentum.

Question: 71

What will be the tension in a rope pulled from its ends by two opposite force 100N each

Answer: 71

71-104

It will be 100N because string is in equilibrium so applied force and reaction force of string of string that is tension are equal.

Question: 72

Define newton's second law of motion and give equation

Answer: 72

72-104

Statement: When a net force acts on a body it produces acceleration in the body in the direction of the net force. The magnitude of this acceleration is directly proportional to the net force acting on the body and inversely proportional to its mass

Equation: F=ma

Question: 73

Write two ways to reduce friction

Answer: 73

73-104

Methods of reducing friction

Making the sliding surfaces smooth

Lubricating the sliding surfaces

Using ball bearings to convert sliding into rolling

Reduce the forces acting on the surface

Question: 74

Action and reaction are always equal and opposite

Answer: 74

74-104

Action and reaction are equal in magnitude but opposite in direction Action and reactioin do not act on the same body Action is applied on one body due to which an equal and opposite reaction is action on another body. Both of these do not neutralize each other due to which the body will move

Question: 75

How does oiling the moving parts of a machine lower friction

Answer: 75

75-104

As the friction of liquids is less than friction of solids. So oiling the moving parts of the machines lower the friction.

Question: 76

What is different between

Answer: 76

76-104

Mass and Weight ,Action and Reaction, Sliding and Rolling Friction

Question: 77

Find the acceleration that is produced by 20N force in a mass of 8kg

Answer: 77

77-104

m=8kg

f=20N

a=?

Using the formula of mass force acceleration

Question: 78

Why spinner of washing machine is made to spin at very high speed

Answer: 78

78-104

Because when it spins at high speed the water from wet clothes is forces out through hole due to lack of centripetal force.

Question: 79

Calculate the value of force acting on a body of mass 4kg and produces and acceleration of 2ms

Answer: 79

79-104

mass=m=4kg

Acceleration=a=2ms

Force=F=?

Question: 80

Is there a reaction in above example

Answer: 80

80-104

Yes there is reaction and its direction is in upward direction

Question: 81

State first law of motion

Answer: 81

81-104

A body continues its state of rest or of uniform motion in a straight line provided no net force acts. on it. It is also called law of inertia.

Question: 82

When a gun is fired it recoils

Answer: 82

82-104

As the gun is fired bullet shoots out of the gun and acquires momentum, To conserve momentum of the system, the gun recoils.

Question: 83

Find the acceleration that is produced by a 20N force in a mass of 8 kg

Answer: 83

83-104

Given Data; m= 8kg

F=20 N

Question: 84

State Newton first law of motion

Answer: 84

84-104

A body continues its state of rest or of uniform motion in a straight line unless acted upon by a net force.

Question: 85

Describe ways to reduce friction.

Answer: 85

85-104

The friction can be reduced by

Making the sliding surface's smooth

Making the fast moving objects a streamline shape (fish shape) such as cars, aero planes etc. This causes the smooth flow of air and thus minimizes air resistance at high speeds.

Lubricating the sliding surfaces.

Using ball bearings or roller bearings because the rolling friction is lesser than the sliding friction.

Question: 86

What is Atwood Machine

Answer: 86

86-104

Atwood machine: Atwood machine is a system consist of two different masses hanging vertically by the ends of a string passing over a pulley

Question: 87

To weight of a body 147N. What its mass

Answer: 87

87-104

Given Data Weight =w=147N

Gravitational acceleration= g=10ms

mass=m=?

w=mg

Question: 88

What will be the tension in a string that is pulled from its ends by two opposite forces 100N each

Answer: 88

88-104

Because force are acting at opposite direction, therefore the net tension is 100N

Question: 89

State newton's third law of motion and wite two examples

Answer: 89

89-104

Newton's third law of motion: To every action there is always an eual but opposite reaction.

Question: 90

Why friction opposes motion

Answer: 90

90-104

Definition: The force that apposes the motion of moving objects is called friction

Question: 91

Define weight and write its unit

Answer: 91

91-104

Weight: Weight of a body is due to the force of gravity acted on it weight of body is eual to the force with which Earth attract it.

Question: 92

Write two difference of Mass and Weight.

Answer: 92

92-104

Mass: Mass of a body is the quantity of matter that it possesses.

It is a scalar quantity

It does not change by using the place

Mass is denoted by m.

Mass can be find by

formula m=f/m

Unit of mass is kilogram (kg)

Question: 93

State the principle of motion of Rocket

Answer: 93

93-104

A rocket moves on the principle of newton's third law of motion When its fuel burns hopt gases escape out from its tail with a very high speed The reaction of these gases on the rocket causes it to move opposite to the gases rushing out of it to move opposite to the gasses rushing out of its tail.

Question: 94

Define centripetal force and centrifugal force.

Answer: 94

94-104

Centripetal force: Centripetal force is a force that keeps a body in a circle.

Equation: F=mv/r

Question: 95

What is the relation between force and momentum

Answer: 95

95-104

The rate of change of momentum of a body is equal to applied force

Equation: F=p1-p1/t

Question: 96

What is meant by tension in a string

Answer: 96

96-104

The force acting along a string is called tension in a string

Question: 97

Why the spanner of washing machine is moved fastly

Answer: 97

97-104

The dryer of the washing machine works on the principle of centrifuge. The dryer consists of a long cylinder with hundreds of small holes on its walls wet clothes are piled up in this cylinder when the cylinder is rotated rapidly about its axis water from wet clothes moves outwards to the wall of the cylinder and is drained out through the holes and the clothes become dry quickly

Question: 98

Describe braking and skidding

Answer: 98

98-104

Braking: The force that acts on a moving vehicle to lock up its types is called braking

Question: 99

Writer two disadvantages and two disadvantages of friction.

Answer: 99

99-104

Advantages of friction: It cannot not written if there would be no friction between paper and pencil

Friction enables us to walk on ground We cannot run on a slippery ground because it offers very little friction.

Question: 100

What is meant by limiting friction

Answer: 100

100-104

Limiting Friction: The maximum value of friction is know as the force of limiting friction

Question: 101

How cream separator work

Answer: 101

101-104

Cream separate is a high-speed spinner which acts on the principle of centrifuge machines. The bowl spins at very high speed causing the heavier contents of milk to move outward in the bowl pushing the lighter contents inward towards the spinning axis. Therefore, skimmed milk, which is denser than cream is collected at the outer wall of the bowl the lighter part (cream) is pushed towards the center from where it is collected through pipe

Question: 102

Action and reaction are always equal and oposite then how does a body move

Answer: 102

102-104

Action and reaction are always equal and opposite in direction even then body also moves, it is due to that action and reaction on different bodies.

Question: 103

What is meant by Force of Limiting Friction symbol

Answer: 103

103-104

Friction: The force that opposes the motion of moving object is called friction.

Question: 104

How does oiling the moving parts of a machine low as friction

Answer: 104

104-104

By applying lubricants (oil or grease) to surfaces they become smooth and friction is reduced As the friction of liquids is less than that of solid surfaces, therefore, oil or grease is applied between the parts of machinery

Physics Chapters

9th Class Chapter 3 Physics Short Questions

0

Perparation Level