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This mock test of Force & Laws Of Motion - MCQ Test (22-11-2017) for Class 9 helps you for every Class 9 entrance exam.
This contains 30 Multiple Choice Questions for Class 9 Force & Laws Of Motion - MCQ Test (22-11-2017) (mcq) to study with solutions a complete question bank.
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QUESTION: 1

Identify the incorrect statement.

Solution:

The spring force is the force exerted by a compressed or stretched spring upon any object that is attached to it. An object that compresses or stretches a spring is always acted upon by a force that restores the object to its rest or equilibrium position. So, the spring force does not always pushes a body.

QUESTION: 2

Some of the leaves may get detached from a tree if we vigorously shake its branch because of

Solution:

If a branch of a tree is vigorously shaken, some of the leaves may get detached from tree due to inertia of rest. The leaves tend to remain in rest but branches come in motion.

QUESTION: 3

Essential characteristic of equilibrium is

Solution:

At equilibrium, the acceleration is equal to zero. So, there is no net change in acceleration of the moving body.

QUESTION: 4

“Inflated balloon lying on the surface of a floor moves forward when pierced with a pin. The above mentioned phenomena is due to

Solution:

Inflated balloon lying on the surface of a floor moves forward when pierced with a pin due to Newton’s third law of motion. The air coming out of the balloon forces the balloon in opposite direction.

QUESTION: 5

How much force acts on body whose momentum is constant (i.e. = constant)?

Solution:

Force is the rate of change of momentum. So, momentum is constant when force is zero.

QUESTION: 6

Inertia is the property of a body by virtue of which the body is

Solution:

This law has two parts, the first part is giving us the concept of inertia while the second part helps us in defining the force. The first part indicates that if a body is at rest, then it can not start moving by itself. Similarly if the body is in state of uniform motion in a straight line can not increase or decrease its velocity or can not change the direction by itself. Thus each body has inability to change the state of rest or state of uniform motion along straight line by itself this inherent property of body is called inertia of a body. The inertia of a body depends on mass of the body. Thus mass is measure of inertia of a body. The second part of law helps us in defining the force. In first part we have seen that a body can not change its state of motion on its own but some external physical quantity is required to do so. This external physical quantity which is required to change the state of motion of a body is called force.

QUESTION: 7

To every action there is an,

Solution:

To every action, there is an equal and opposite reaction. This is the newton’s third law of motion.

QUESTION: 8

The change in the momentum of a body in 0.01 second is 10 kg ms-1. The force acting on this body is1.

Solution:

The force acting on a body is equal to rate of change of momentum. Change of momentum = 10 Kg/s, time taken = 0.01 second. Force = 10/0.01 = 1000N.

QUESTION: 9

Which of the Expression to find the Force is correct ?

Solution:

QUESTION: 10

Which has more inertia?

Solution:

Inertia of the body is proportional to the mass of the body. 5Rs coin is heavier than 5Rs note and 1Rs coins. So, inertia of 5Rs coin more than others.

QUESTION: 11

“Forces always occur in pairs”. From which law can we conclude the above statement?

Solution:

The force always occurs in pairs. According to third law of motion, there is equal and opposite reaction. So two force, action and reaction acts in pair always.

QUESTION: 12

**Statement A :** Rocket can propel its self in vacuum.

**Statement B :** Newton’s laws are universal.

Which of the two statements is true?

Solution:

Rocket moves forward according to newton’s third law of motion. The gas and other substance coming out from the tail push the rocket in forward direction. Newton’s laws are universal.

QUESTION: 13

10^{5} dyne is equal to

Solution:

One Newton (1N) is equal to 105 dyne. Both dyne and Newton is unit of force.

QUESTION: 14

A high jumper runs for a while before taking high jump so that the inertia of __________ help him in taking a long jump.

Solution:

A high jumper runs for a while before taking high jump so that the inertia of motion help him in taking a long jump. Inertia of motion tends to remain in state of motion.

QUESTION: 15

Frictional force

Solution:

Frictional force always opposes relative motion between the surfaces of contact. The direction of force is always in opposite direction.

QUESTION: 16

A ball is dropped from a height of 10m. Ball is embedded in sand of 1m and stops.

Solution:

When body is dropped from height, the potential energy deceases and kinetic energy increases. A ball dropped from height will conserve only kinetic energy.

QUESTION: 17

A force has

Solution:

A force has both magnitude as well as direction. Force is a vector quantity. Force is the product of mass and acceleration.

QUESTION: 18

If P and Q are two bodies with masses 10 kg and 5kg respectively, then which body has more inertia?

Solution:

The inertia of the body is proportional to mass of the body. So, body P with masses 10 kg will have more inertia in comparison to body Q of mass 5 kg.

QUESTION: 19

‘Any two forces which are equal and opposite form an action and reaction pair’ The above statement is

Solution:

The two forces acting on same body, which are equal and opposite direction forms action and reaction. This is the newton’s thirds law of motion.

QUESTION: 20

Two bodies of masses 1kg and 5kg are dropped gently from the top of a tower. At a point 50cm from the ground both the bodies will have the same

Solution:

The velocity of the body falling towards depends upon gravitational force acting on it. So, both the body of masses 1 kg and 5 kg will have same velocity at particular height and fall at same time at the ground.

QUESTION: 21

**Statement A :** Gravitational force is the weakest force in nature

**Statement B :** Electrostatic force is the example of non – contact force

Which of the above two statement is true?

Solution:

Gravitational force is very weak force as it depends upon mass of the body and distance between two objects. Electrostatic force is non-contact force.

QUESTION: 22

In a football and stone of same size, the inertia of

A Football is greater

B Football is lesser

C Stone is greater

D Stone is lesser

Solution:

QUESTION: 23

“Action and reaction are equal and opposite but even then they do not cancel each other” the above statement is

Solution:

Action and reaction are equal and opposite but even they do not cancel each other because they acts in opposite direction. Hence the statement is correct.

QUESTION: 24

**Statement A :** Calculus, a new branch of mathematics was stated by Newton.

**Statement B :** If mass remains same, doubling the force will reduce the acceleration to half.

Which of the above two statements is true

Solution:

The branch of mathematics, called Calculus was stated by Newton. Force is the product of mass and acceleration. So, acceleration= force /mass. Doubling of force will increase the acceleration if mass is kept same.

QUESTION: 25

Ayush hits a cricket ball which than rolls of a level ground after covering a short distance, the ball comes to rest. The ball slows to a stop because

Solution:

The ball moving on level ground comes to rest after covering a short distance due to frictional force acting on it. So, ball slows to a stop because there is a force on the ball opposing the motion.

QUESTION: 26

Dust particles come out of a hanging carpet when we strike it with a stick because-

A Carpet starts moving forward and backward due to inertia of motion

B Dust particles remain at rest

C Dust particles starts moving forward due to inertia of motion

D Carpet remains at rest

Solution:

QUESTION: 27

Find the incorrect statement about Newton’s law of action and reaction. Action and reaction

Solution:

Newton’s third law of motion explains action and reaction. Action and reaction acts simultaneously, are equal in magnitude. They act on different direction and acts on different body.

QUESTION: 28

If an object experiences a net zero unbalanced force, than the body

Solution:

If an object experience a net zero unbalanced force, than the body moves with constant velocity. Zero unbalanced force due to produce acceleration in the body.

QUESTION: 29

The physical quantity which is equal to the rate of change of momentum is

Solution:

Force is the equal to the rate of change of momentum. Force = final momentum-initial momentum/time , f = mv-mu/t.

QUESTION: 30

Which of the following is not used to reduce friction

Solution:

To reduce the friction, oiling between contact surface, using ball bearing and using grease between contact surfaces. Making scratches between contact surfaces increase the friction.

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