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# 9th Class Chapter 3 Physics Short Questions

An important facility for 9th class students preparing for short questions physics 9th class chapter 3 of BISE. Get hundreds of questions to prepare and get better marks in 9th physics ### 0

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##### Question: 1
Define Momentum.
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 Braking force.
2-104
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: 3
Define Tension in a string:
3-104
The force acting along a string is called tension. Its unit is newton . It is represented by 'T'
##### Question: 4
Define Circular motion:
4-104
If a body move in circular path its motion is known as circular motion.
##### Question: 5
Define friction.
5-104
The force that opposes the motion of moving object is called friction.
##### Question: 6
6-104
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: 7
Define Cream separator:
7-104
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: 8
Difference between Mass or Weight.
8-104
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: 9
Why is it dangerous o travel on the roof of a bus
9-104
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: 10
Why is it dangerous to travel on the roof of a bus.
10-104
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: 11
What is different between
11-104
Mass and Weight ,Action and Reaction, Sliding and Rolling Friction
##### Question: 12
What is inertia
12-104
Inertia of a body is its property due to which it resists any change in its state of rest or motion
##### Question: 13
What is the law of inertia?
13-104
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: 14
Define net force.
14-104
Net force is the resultant of all forces acting on a body.
##### Question: 15
why do passengers fall outward of the bus when a bus takes a sharp turn
15-104
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: 16
Difference between sliding friction and Rolling friction.
16-104
Sliding friction: In sliding friction the surface of a body moves by sliding against the surface of another body.
##### Question: 17
Define centripetal force and give formula
17-104
Centripetal force is a force that keeps a body to move in a circle.
##### Question: 18
State first law of motion.
18-104
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: 19
Define unit of force.
19-104
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: 20
What is the law of inertia
20-104
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: 21
What is isolated system.
21-104
An isolated system is a group of interacting bodies on which no external force is acting.
##### Question: 22
How can you relate a force with the change of momentum of a body
22-104
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: 23
What is meant by sliding friction.
23-104
When two bodies slid over one another, the force of friction between them is known as sliding friction.
##### Question: 24
What will be the tension in a rope pulled from its ends by two opposite force 100N each
24-104
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: 25
Write two method of reducing friction.
25-104
Making the sliding surfaces smooth By converting sliding friction into rolling friction.
##### Question: 26
Action and reaction are always equal and opposite
26-104
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: 27
Define limiting frictions.
27-104
The maximum value of static friction is known the force of limiting friction Fs=μmg
##### Question: 28
What is force
28-104
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: 29
What is action in above example.
29-104
Action is weight of book acting downward on the table.
##### Question: 30
Why is it easy to roll a cylindrical eraser on a paper sheet than to slide it?
30-104
Because the sliding friction is greater than rolling friction. So rolling is easy than sliding .
##### Question: 31
What do you know about following
31-104
Tension in a string, Banking of roads, Braking force, Cream separator.
##### Question: 32
What is meant by rolling friction?
32-104
The force of friction between a rolling body and a surface over which it rolls is called rolling friction.
##### Question: 33
Describe two situations in which force of friction is needed
33-104
We cannot rite without friction between paper and the pencil
We cannot walk without friction Friction enables us to walk on the ground.
##### Question: 34
What are the factor on which friction depends?
34-104
Nature of two surfaces in contact pressing force between the surfaces in contact.
##### Question: 35
Describe ways to reduce friction.
35-104
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: 36
What do you mean by skidding ?
36-104
Motion of wheel without rotation is called skidding.
##### Question: 37
Why is the law of conservation of momentum important
37-104
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: 38
How does oiling the moving parts of a machine lower friction
38-104
As the friction of liquids is less than friction of solids. So oiling the moving parts of the machines lower the friction.
##### Question: 39
Find the acceleration that is produced by 20N force in a mass of 8kg
39-104
m=8kg
f=20N
a=?
Using the formula of mass force acceleration
##### Question: 40
Define friction and write equation.
40-104
The force that opposes the motion of moving objects is called friction. Fs=μmg
##### Question: 41
State newton's third law of motion.
41-104
To every action there is alwasys an equal but opposite reaction e.g. a launching of rocket.
##### Question: 42
A horse pushes the cart It the action and reaction are equal and opposite then how does the cart move.
42-104
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: 43
What is meant by centrifugal force.
43-104
The reaction of centripetal force is called centrifugal force. Fc=mv2/r
##### Question: 44
What is an Atwood machine
44-104
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: 45
Why rolling friction is less than sliding friction
45-104
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: 46
What is meant by dynamics?
46-104
The branch of mechanics that deals with study of motion of an object and the cause of its motion is called dynamics.
##### Question: 47
What would happen if all friction disappears
47-104
If all friction disappears, there will be no existence of life.
##### Question: 48
Define Newton's second law.
48-104
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: 49
Why spinner of washing machine is made to spin at very high speed
49-104
Because when it spins at high speed the water from wet clothes is forces out through hole due to lack of centripetal force.
##### Question: 50
State Newton first law of motion
50-104
A body continues its state of rest or of uniform motion in a straight line unless acted upon by a net force.
##### Question: 51
State first law of motion
51-104
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: 52
What is Atwood Machine
52-104
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: 53
What is meant by tension in a string
53-104
The force acting along a string is called tension in a string
##### Question: 54
What is the difference between action and reaction
54-104
Action: The force exerted by external agency on a system is called action.
##### Question: 55
Calculate the value of force acting on a body of mass 4kg and produces and acceleration of 2ms
55-104
mass=m=4kg
Acceleration=a=2ms
Force=F=?
##### Question: 56
Find the acceleration that is produced by a 20N force in a mass of 8 kg
56-104
Given Data; m= 8kg
F=20 N
##### Question: 57
State the principle of motion of Rocket
57-104
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: 58
To weight of a body 147N. What its mass
58-104
Given Data Weight =w=147N
Gravitational acceleration= g=10ms
mass=m=?
w=mg
##### Question: 59
When a gun is fired, it recoils.
59-104
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: 60
What is action in above example
60-104
Action is weight of book acting downward on the table.
##### Question: 61
Define newton's second law of motion and give equation
61-104
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: 62
Define weight and write its unit
62-104
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: 63
Define centripetal force and centrifugal force.
63-104
Centripetal force: Centripetal force is a force that keeps a body in a circle.
Equation: F=mv/r
##### Question: 64
Define sliding friction and rolling friction?
64-104
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: 65
Action and reaction are always equal and oposite then how does a body move
65-104
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: 66
State Newton third law of Motion?
66-104
To every action there is always an equal but opposite reaction
##### Question: 67
Differentiate between sliding friction and rolling friction.
67-104
Sliding friction: The frictional force produced between a body and surface when it rotates on the surface is called sliding friction.
##### Question: 68
Define inertia. Describe two of inertia.
68-104
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: 69
What will be the tension in a string that is pulled from its ends by two opposite forces 100N each
69-104
Because force are acting at opposite direction, therefore the net tension is 100N
##### Question: 70
Action and reaction are always equal and opposite. Then how does a body moves?
70-104
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: 71
Stretch out your palm and hold a book on it. How much force you neend to prevent the book from falling
71-104
We need a force equal to the weight of book to prevent it from falling
##### Question: 72
What is meant by limiting friction
72-104
Limiting Friction: The maximum value of friction is know as the force of limiting friction
##### Question: 73
Why is it dangerous to travel at the roof of a bus
73-104
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: 74
Write two difference of Mass and Weight.
74-104
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: 75
Define newton, Circular motion?
75-104
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: 76
What is the relation between force and momentum
76-104
The rate of change of momentum of a body is equal to applied force
Equation: F=p1-p1/t
##### Question: 77
Is there a reaction in above example
77-104
Yes there is reaction and its direction is in upward direction
##### Question: 78
Find the acceleration produced by a force of 100N in a mass of 50kg
78-104
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: 79
When a gun is fired it recoils
79-104
As the gun is fired bullet shoots out of the gun and acquires momentum, To conserve momentum of the system, the gun recoils.
##### Question: 80
What is meant by Force of Limiting Friction symbol
80-104
Friction: The force that opposes the motion of moving object is called friction.
##### Question: 81
How does oiling the moving parts of a machine low as friction
81-104
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
##### Question: 82
What would happen if all friction suddenly disappears?
82-104
If all friction suddenly disappears, everyone dies because you can'twalk or do anything.
##### Question: 83
When a gun is fired, it recoils, Why?
83-104
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: 84
Why the spanner of washing machine is moved fastly
84-104
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: 85
State Newton Second Law of motion?
85-104
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: 86
Difference between kinematics and Dynamic?
86-104
Kinematics is the study of motion and position, or the geometry of an event.
##### Question: 87
A horse pushes the cart. If the action and reaction are equal and opposites,then how does the cart move?
87-104
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: 88
88-104
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: 89
A force of 20n moves a body with an acceleration of 2
89-104
Given data Force=F=20N
acceleration =a=2ms
m=?
We know that f=ma
##### Question: 90
How cream separator work
90-104
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: 91
In which case it is easy for the tireto roll over? Rough ground
91-104
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: 92
Define Coefficient offriction, cream separator, banking of road?
92-104
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: 93
Define Tension in a string, Braking force Momentum?
93-104
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: 94
State newton's third law of motion and wite two examples
94-104
Newton's third law of motion: To every action there is always an eual but opposite reaction.
##### Question: 95
Why friction opposes motion
95-104
Definition: The force that apposes the motion of moving objects is called friction
##### Question: 96
96-104
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: 97
A force of 20N moves a body with an acceleration of 2ms-2What is tits mass?
97-104
F= 20N
a= 2ms-2
m=?
F=maor m= F/a
m=20/2=10kg
Mass is 10 kg
##### Question: 98
Which shoes is better for jugging
98-104
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: 99
Difference between Mass and Weight?
99-104
Mass
1- Mass of a body is the quantity of matter possessed by the body
2- It is a scalar quantity
##### Question: 100
Write two ways to reduce friction
100-104
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: 101
Describe braking and skidding
101-104
Braking: The force that acts on a moving vehicle to lock up its types is called braking
##### Question: 102
Action and reaction are always equal and opposite. Then how does a body moves?
102-104
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: 103
What will be the tension in a ropethat is pull from its ends by two opposite forces 100N?