## Class 9 Science Objective Chapter – 9  Force and Laws of Motion

Here we are providing Class 9 Science Objective Chapter – 9  Force and Laws of Motion because its very important for Class 9 students as we all know that every board exam question has MCQs so that students should practice these questions so that students can get good marks in board. Class 9 Science Objective Chapter – 9  Force and Laws of Motion is an extremely important and its also a year in which students learn the fundamentals of concepts that help them lay a solid foundation for their higher education. Here we are providing in Class Class 9 Science Objective Chapter – 9  Force and Laws of Motion 100+ questions  so that students practice more and more. If you want class wise Notes Then Click Here

## Class 9 Science Objective Chapter – 9  Force and Laws of Motion

1.Which of the following statements is not correct for an object moving along a straight path in an accelerated motion?

( A ) Its speed keeps changing

( B ) Its velocity always changes

( C ) It always goes away from the Earth

( D ) A force is always acting on it

Ans – ( D )

2. 1-kg object is lying on the ground. An unbalanced force of magnitude 1 N is applied to the object. Which of these options explains the motion of the object as a result of the acting force?

( A ) The object will accelerate in the direction of the applied force.

( B ) The object will accelerate in a direction perpendicular to the applied force.

( C ) The object will decelerate in the direction of the applied force.

( D ) The object will remain at rest

Ans – ( A )

3. Newton’s second law of motion is ________.

( A ) F = mv

( B ) F = p2 – p1 t2 – t1

( C ) F = v2 – v1 t2 – t1

( D ) F = s2 – s1 t2 – t1

Ans – ( A )

4.A goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to

( A ) exert larger force on the ball

( B ) reduce the force exerted by the balls on the hands

( C ) increase the rate of change of momentum

( D ) decrease the rate of change of momentum

Ans – ( D )

5.  A passenger in a moving train tosses a coin which falls behind him. It means that the motion of the train is

( A ) accelerated

( B ) uniform

( C ) retarded

( D ) along circular tracks

Ans – ( A )

6.The unit of measuring the momentum of a moving body is:

( A ) m/s

( B ) kg.m/s

( C ) kg.m/s2

( D ) N m2/kg2

Ans – ( B )

7. —- is responsible for change in magnitude of speed.

( A ) Momentum

( B ) Force

( C ) Inertia

( D ) Kinetic energy.

Ans – ( B )

8.According to the third law of motion, action and reaction

( A ) always act on the same body

( B ) always act on different bodies in opposite directions

( C ) have same magnitude and directions

( D ) act on either body at normal to each other

Ans – ( B )

9. In the absence of external force the velocity —–.

( A ) Remains constant.

( B ) Vanishes.

( C ) Changes continuously.

( D ) None of these.

Ans – ( A )

10.A water tank filled upto 2/3 of its height is moving with a uniform speed. On sudden application of the brake, the water in the tank would

( A ) Move backward

( B ) Move forward

( C ) Come to the rest

( D ) Be unaffected

Ans – ( B )

11.A goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to

( A ) exert larger force on the ball

( B ) reduce the force exerted by the balls on the hands

( C ) increase the rate of change of momentum

( D ) decrease the rate of change of momentum

Ans – ( D )

12. Newton’s first law introduces the concept of —-.

A) Momentum

( B ) Inertia

( C ) Conservation of energy.

( D ) Action and reaction.

Ans – ( B )

13.According to the third law of motion, action and reaction

( A ) always act on the same body

( B ) always act on different bodies in opposite directions

( C ) have same magnitude and directions

( D ) act on either body at normal to each other

Ans – ( B )

14.The inertia of an object tends to cause the object

( A ) to increase its speed

( B ) to decrease its speed

( C ) to resist any change in its state of motion

( D ) to decelerate due to friction

Ans – ( C )

15. Which object has greater inertia.

( A ) Rubber ball

( B ) Gas cylinder

( C ) Bicycle

( D ) Truck

Ans – ( D )

16.A passenger in a moving train tosses a coin which falls behind him. It means that motion of the train is

( A ) accelerated

( B ) uniform

( C ) retarded

( D ) along circular tracks

Ans – ( A )

17. The seat belts are provided in the cars so that if the car stops suddenly due to an emergency braking, the persons sitting on the front seats are not thrown forward violently and saved from getting injured. Can you guess the law due to which a person falls in forward direction on the sudden stopping of the car?

( A ) Newton’s first law of motion

( B ) Newton’s second law of motion

( C ) Newton’s third law of motion

( D ) Newton’s law of gravitation

Ans – ( A )

18. A water tank filled upto 2/3 of its height is moving with a uniform speed. On sudden application of the brake, the water in the tank would

( A ) Move backward

( B ) Move forward

( C ) Come to the rest

(e) Be unaffected

Ans – ( B )

19.An object of mass 2 kg is sliding with a constant velocity of 4 ms-1 on a frictionless horizontal table. The force required to keep the object moving with the same velocity is

( A ) 32 N

( B ) 0 N

( C ) 2 N

( D ) 8 N

Ans – ( B )

20. The seat belts are provided in the cars so that if the car stops suddenly due to an emergency braking, the persons sitting on the front seats are not thrown forward violently and saved from getting injured. Can you guess the law due to which a person falls in forward direction on the sudden stopping of the car?

( A ) Newton’s first law of motion

( B ) Newton’s second law of motion

( C ) Newton’s third law of motion

( D ) Newton’s law of gravitation

Ans – ( A )

21.Rocket works on the principle of conservation of

( A ) mass

( B ) energy

( C ) momentum

( D ) velocity

Ans – ( C )

22. The speed of a car weighing 1500 kg increases from 36 km/h to 72 km/h uniformly. What will be the change in momentum of the car?

( A ) 15000 kg km/h

( B ) 15000 kg m/s

( C ) 54000 kg m/s

( D ) 54000 g m/s

Ans – ( B )

23.A water tanker filled up to 23 of its height is moving with a uniform speed. On a sudden application of brakes, the water in the tank would

( A ) move backward

( B ) move forward

( C ) be unaffected

( D ) rise upwards

Ans – ( B )

24. A man wearing a bullet-proof vest stands on roller skates. The total mass is 80 kg. A bullet of mass 20 g is fired at 400 m/s. It is stopped by the vest and falls to the ground. What is then the velocity of the man?

( A ) 1 m/s

( B ) 0.1 m/s

( C ) 0.01 m/s

( D ) 0 m/s

Ans – ( B )

25.If the mass of a body is doubled and its velocity becomes half, then the linear momentum of the body will

( A ) remain same

( B ) become double

( C ) become half

( D ) become four times.

Ans – ( A )

26. Inertia depends upon –

( A ) acceleration of the body

( B ) velocity of the body

( C ) shape of the body

( D ) mass of the body

Ans – ( D )

27.When a number of forces acting simultaneously on a body bring about a change in its state of rest or of uniform motion in a straight line, then these forces acting on the body are said to be

( A ) balanced forces

( B ) equal forces

( C ) unbalanced forces

( D ) opposite forces

Ans – ( D )

28. Forces of action and reaction are:

( A ) equal and in same direction

( B ) equal and in opposite direction

( C ) unequal and in same direction

( D ) unequal and opposite.

Ans – ( B )

29.When a car at high speed makes a sharp turn, the driver in a car tends to get thrown to the side opposite to the turn. This is due to the

( A ) inertia of motion

( B ) inertia of time

( C ) inertia of rest

( D ) inertia of direction

Ans – ( A )

30. If the action and reaction were to act on the same body-

( A ) the resultant would be zero

( B ) the body would not move at all

( C ) both A and B are correct

( D ) neither A nor B is correct

Ans – ( C )

31.A man is standing on a boat in still water. If he walks towards the shore, then the boat will

( A ) move away from the shore

( B ) move towards the shore

( C ) remain stationary

( D ) none of these

Ans – ( A )

32. Consider two spring balances hooked as shown in the figure. We pull them in opposite directions. If the reading shown by A is 1.5 N, the reading shown by B will be – A B

( A ) 1.5 N

( B ) 2.5 N

( C ) 3.0 N

( D ) zero

Ans – ( A )

33.Which of the following is an incorrect statement?

( A ) Mass is measure of inertia of a body.

( B ) Newton’s first law of motion is the law of inertia.

( C ) Unbalanced force produces constant velocity.

( D ) Newton’s third law talks about the direction of the force.

Ans – ( C )

34. A plate, a ball and a child all have the same mass. The one having more inertia is the

( A ) plate

( B ) ball

( C ) child

( D ) All have equal inertia

Ans – ( D )

35.A ball is thrown vertically upward in a train moving with uniform velocity. The ball will

( A ) fall behind the thrower

( B ) fall ahead of the thrower

( C ) return back to the thrower

( D ) fall on the left of the thrower

Ans – ( C )

36. The inertia of an object tends to cause the object

( A ) to increase its speed

( B ) to decrease its speed

( C ) to resist any change in the state of rest or of motion

( D ) to decelerate due to friction

Ans – ( C )

37.Which of the following is not an application of conservation of linear momentum?

( A ) While firing a bullet, the gun must be held tight to the shoulder

( B ) When a man jumps from a boat to the shore

( C ) A rocket explodes on midway from the ground

( D ) A body suspended from the hook of a spring balanced in a lift which is accelerated downward

Ans – ( C )

38. When unbalanced forces act on a body, the body:

( A ) Must move with uniform velocity

( B ) Must remain at rest

( C ) Must experience acceleration

( D ) Must move in a curved path

Ans – ( C )

39.When we stop pedalling, the bicycle begins to slow down. This is because of the

( A ) Frictional force acting along the direction of motion of bicycle

( B ) Air resistance which is in the direction of motion

( C ) Frictional force acting opposite to the direction of motion of bicycle by the road

( D ) Nature of the bicycle to stop after some time

Ans – ( D )

40. A man throws a ball weighing 200 g vertically upwards with a speed of 10m/s. Its momentum at the highest point of its flight will be:

( A ) 2 kg. m/s

( B ) 2000 kg.m/s

( C ) Insufficient data to find the momentum.

( D ) zero

Ans – ( D )

41.Inertia is the property of a body by virtue of which, it cannot change by itself

( A ) its state of rest

( B ) its steady state of uniform motion

( C ) its direction of motion

( D ) all of these.

Ans – ( D )

42. A force of ‘P* N acts on a particle so as to accelerate it from rest to a velocity ‘v’ m/s. The force ‘P’ is then replaced by ‘Q’ N which decelerates it to rest.

( A ) P may be equal to Q

( B ) P must be equal to Q

( C ) P must be unequal to Q

( D ) none of these

Ans – ( A )

43.An athlete does not come to rest immediately after crossing the winning line due to the

( A ) inertia of motion

( B ) inertia of rest

( C ) inertia of direction

( D ) none of these

Ans – ( A )

44. When a force is exerted on an object, it can change its:

( A ) State

( B ) Position

( C ) Shape

( D ) All the above

Ans – ( D )

45.A bullet of mass A and velocity B is fired into a wooden block of mass C. If the bullet gets embedded in the wooden block, then the magnitude of velocity of the system just after the collision will be

( A ) A+BAC

( B ) A+CB+C

( C ) ACB+C

( D ) ABA+C

Ans – ( D )

46. What force can change the velocity of a body of mass 1kg from 20 m/s to 30m/s in 2 seconds?

( A ) 10 N

( B ) 15 N

( C ) 5 N

( D ) 25 N

Ans – ( C )

47.The masses of two bodies are in ratio 5 : 6 and their velocities are in ratio 1 : 2. Then their linear momentum will be in the ratio

( A ) 5 : 6

( B ) 1 : 2

( C ) 12 : 5

( D ) 5 : 12

Ans – ( D )

48.One way that you can recognize that a force is acting on an object:

( A ) is to note any change in the objects state of motion.

( B ) is to determine its mass at different locations.

( C ) is to measure the instantaneous velocity of a moving object.

( D ) A and C

Ans – ( A )