# MCQs For NCERT Class 11 Physics Chapter 5 Laws of Motion

Please refer to the MCQ Questions for Class 11 Physics Chapter 5 Laws of Motion with Answers. The following Laws of Motion Class 11 Physics MCQ Questions have been designed based on the latest syllabus and examination pattern for Class 11. Our experts have designed MCQ Questions for Class 11 Physics with Answers for all chapters in your NCERT Class 11 Physics book.

## Laws of Motion Class 11 MCQ Questions with Answers

See below Laws of Motion Class 11 Physics MCQ Questions, solve the questions and compare your answers with the solutions provided below.

Question. Centripetal force :
(a) can change speed of the body.
(b) is always perpendicular to direction of motion
(c) is constant for uniform circular motion.
(d) all of these

B

Question. When a horse pulls a cart, the horse moves down to
(a) horse on the cart.
(b) cart on the horse.
(c) horse on the earth.
(d) earth on the horse.

D

Question. A 4000 kg lift is accelerating upwards. The tension in the supporting cable is 48000 N. If g = 10ms-2 then the acceleration of the lift is
(a) 1 ms-2
(b) 2 ms-2
(c) 4 ms-2
(d) 6 ms-2

B

Question. A rocket has a mass of 100 kg. Ninety percent of this is fuel. It ,ejects fuel vapors at the rate of 1 kg/sec with a velocity of 500 m/sec relative to the rocket. It is supposed that the rocket is outside the gravitational field. The initial upthrust on the rocket when it just starts moving upwards is
(a) zero
(b) 500 newton
(c) 1000 newton
(d) 2000 newton

B

Question. A 0.1 kg block suspended from a massless string is moved first vertically up with an acceleration of 5ms-2 and then moved vertically down with an acceleration of 5ms-2 . If T1 and T2 are the respective tensions in the two cases, then
(a) T2 > T1
(b) T1 – T2 = 1 N, if g = 10ms-2
(c) T1 -T2 = 1kg f
(d) T1 – T2 = 9.8N, if g = 9.8 ms-2

B

Question. The force of action and reaction
(a) must be of same nature
(b) must be of different nature
(c) may be of different nature
(d) may not have equal magnitude

A

Question. A body is moving with uniform velocity, then
(a) no force must be acting on the body.
(b) exactly two forces must be acting on the body
(c) body is not acted upon by a single force.
(d) the number of forces acting on the body must be even.

C

Question. The direction of impulse is
(a) same as that of the net force
(b) opposite to that of the net force
(c) same as that of the final velocity
(d) same as that of the initial velocity

A

Question. A monkey is climbing up a rope, then the tension in the rope
(a) must be equal to the force applied by the monkey on the rope
(b) must be less than the force applied by the monkey on the rope.
(c) must be greater than the force applied by the monkey on the rope.
(d) may be equal to, less than or greater the force applied by the monkey on the rope.

A

Question. A uniform rope of length L resting on a frictionless horizontal surface is pulled at one end by a force F. What is the tension in the rope at a distance l from the end where the force is applied.
(a) F
(b) F (1 + l/L)
(c) F/2
(d) F (1 – l/L)

D

Question. A mass is hanging on a spring balance which is kept in a lift.
The lift ascends. The spring balance will show in its readings
(a) an increase
(b) a decrease
(c) no change
(d) a change depending on its velocity

A

Question. A particle of mass m moving eastward with a speed v collides with another particle of the same mass moving northward with the same speed v. The two particles coalesce on collision. The new particle of mass 2m will move in the northexternal direction with a velocity :
(a) v/2
(b) 2v
(c) v / 2
(d) None of these

C

Question. A spring is compressed between two toy carts of mass m1 and m2. When the toy carts are released, the springs exert equal and opposite average forces for the same time on each toy cart. If v1 and v2 are the velocities of the toy carts and there is no friction between the toy carts and the ground, then :
(a) v1/v2 = m1/m2
(b) v1/v2 = m2/m1
(c) v1/v2 = –m2/m1
(d) v1/v2 = –m1/m2

C

Question. A rider on a horse back falls forward when the horse suddenly stops. This is due to
(a) inertia of horse
(b) inertia of rider
(c) large weight of the horse
(d) losing of the balance

B

Question. A ball of mass m is thrown vertically upwards. What is the rate at which the momentum of the ball changes?
(a) Zero
(b) mg
(c) Infinity
(d) Data is not sufficient

B

Question. A weight W rests on a rough horizontal plane. If the angle of friction be q , the least force that will move the body along the plane will be
(a) Wcos q
(b) Wcot q
(c) Wtan q
(d) Wsin q

C

Question. A bird is in a wire cage which is hanging from a spring balance . In the first case, the bird sits in the cage and in the second case, the bird flies about inside the cage. The reading
in the spring balance is
(a) more in the first case
(b) less in first case
(c) unchanged
(d) zero in second case.

A

Question. A body of mass 32 kg is suspended by a spring balance from the roof of a vertically operating lift and going downward from rest. At the instant the lift has covered 20 m and 50 m, the spring balance showed 30 kg and 36 kg respectively. Then the velocity of the lift is
(a) decreasing at 20 m, and increasing at 50 m
(b) increasing at 20m and decreasing at 50 m
(c) continuously decreasing at a steady rate throughout the journey
(d) constantly increasing at constant rate throughout the journey.

B

Question. An object at rest in space suddenly explodes into three parts of same mass. The momentum of the two parts are 2piˆ and pˆj . The momentum of the third part
(a) will have a magnitude p√3
(b) will have a magnitude p√ 5
(c) will have a magnitude p
(d) will have a magnitude 2p.

B

Question. A triangular block of mass M with angles 30°, 60°, and 90° rests with its 30°–90° side on a horizontal table. A cubical block of mass m rests on the 60°–30° side. The acceleration which M must have relative to the table to keep m stationary relative to the triangular block assuming frictionless contact is
(a) g
(b) g/√2
(c) g/ √3
(d) g/√5

C

Question. In an explosion, a body breaks up into two pieces of unequal masses. In this
(a) both parts will have numerically equal momentum
(b) lighter part will have more momentum
(c) heavier part will have more momentum
(d) both parts will have equal kinetic energy

A

Question. An object of mass 10 kg moves at a constant speed of 10 ms–1. A constant force, that acts for 4 sec on the object, gives it a speed of 2 ms–1 in opposite direction. The force acting on the object is
(a) –3 N
(b) –30 N
(c) 3 N
(d) 30 N

B

Question. A toy gun consists of a spring and a rubber dart of mass 16 g. When compressed by 4 cm and released, it projects the dart to a height of 2 m. If compressed by 6 cm, the height achieved is
(a) 3 m
(b) 4 m
(c) 4.5 m
(d) 6 m

C

Question. A player stops a football weighting 0.5 kg which comes flying towards him with a velocity of 10m/s. If the impact lasts for 1/50th sec. and the ball bounces back with a velocity of 15 m/s, then the average force involved is
(a) 250 N
(b) 1250 N
(c) 500 N
(d) 625 N

D

Question. A rocket of mass 5000 kg is to be projected vertically upward. The gases are exhausted vertically downwards with velocity 1000 ms–2 with respect to the rocket. What is the minimum rate of burning the fuel so as to just lift the rocket upwards against gravitational attraction ?
(a) 49 kg s–1
(b) 147 kg s–1
(c) 98 kg s–1
(d) 196 kg s–1

A

Question. A 50 kg ice skater, initially at rest, throws a 0.15 kg snowball with a speed of 35 m/s. What is the approximate recoil speed of the skater?
(a) 0.10 m/s
(b) 0.20 m/s
(c) 0.70 m/s
(d) 1.4 m/s

A

Question. A car travelling at a speed of 30 km/h is brought to a halt in 4 m by applying brakes. If the same car is travelling at 60 km/h, it can be brought to halt with the same braking power in
(a) 8 m
(b) 16 m
(c) 24 m
(d) 32 m

B

Question. A body of mass 4 kg moving on a horizontal surface with an initial velocity of 6 ms–1 comes to rest after 3 seconds. If one wants to keep the body moving on the same surface with the velocity of 6 ms–1, the force required is
(a) Zero
(b) 4 N
(c) 8 N
(d) 16 N

C

Question. A machine gun has a mass 5 kg. It fires 50 gram bullets at the rate of 30 bullets per minute at a speed of 400 ms–1. What force is required to keep the gun in position?
(a) 10 N
(b) 5 N
(c) 15 N
(d) 30 N

A

Question. A force of 10 N acts on a body of mass 20 kg for 10 seconds.
Change in its momentum is
(a) 5 kg m/s
(b) 100 kg m/s
(c) 200 kg m/s
(d) 1000 kg m/s

B

Question. Two blocks of masses 2 kg and 1 kg are placed on a smooth horizontal table in contact with each other. A horizontal force of 3 newton is applied on the first so that the block moves with a constant acceleration. The force between the blocks would be
(a) 3 newton
(b) 2 newton
(c) 1 newton
(d) zero

C

Question. The coefficient of friction between two surfaces is 0.2. The angle of friction is
(a) sin-1(0.2)
(b) cos-1(0.2)
(c) tan-1(0.1)
(d) cot -1(5)

D

Question. A man weighing 80 kg is standing on a trolley weighing 320 kg. The trolley is resting on frictionless horizontal rails. If the man starts walking on the trolley along the rails at a speed of one metre per second, then after 4 seconds, his displacement relative to the ground will be :
(a) 5 metres
(b) 4.8 metres
(c) 3.2 metres
(d) 3.0 metres

C

Question. Starting from rest, a body slides down a 45º inclined plane in twice the time it takes to slide down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is:
(a) 0.33
(b) 0.25
(c) 0.75
(d) 0.80

C

Question. Two trolleys of mass m and 3m are connected by a spring.
They were compressed and released at once, they move off in opposite direction and come to rest after covering a distance S1, S2 respectively. Assuming the coefficient of friction to be uniform, ratio of distances S1 : S2 is :
(a) 1 : 9
(b) 1 : 3
(c) 3 : 1
(d) 9 : 1

D

Question. A particle of mass 10 kg is moving in a straight line. If its displacement, x with time t is given by x = (t3 – 2t – 10) m, then the force acting on it at the end of 4 seconds is
(a) 24 N
(b) 240 N
(c) 300 N
(d) 1200 N

B

Question. When forces F1, F2, F3 are acting on a particle of mass m such that F2 and F3 are mutually perpendicular, then the particle remains stationary. If the force F1 is now removed then the acceleration of the particle is
(a) F1/m
(b) F2F3/mF1
(c) (F2 – F3)/m
(d) F2/m

A

Question. A uniform chain of length 2 m is kept on a table such that a length of 60 cm hangs freely from the edge of the table. The total mass of the chain is 4 kg. What is the work done in pulling the entire chain on the table ?
(a) 12 J
(b) 3.6 J
(c) 7.2 J
(d) 1200 J

B

Question. A body of mass 1 kg moving with a uniform velocity of 1ms-1 . If the value of g is 5ms-2 , then the force acting on the frictionless horizontal surface on which the body is moving is
(a) 5 N
(b) 1 N
(c) 0 N
(d) 10N

A

Question. A trailer of mass 1000 kg is towed by means of a rope attached to a car moving at a steady speed along a level road. The tension in the rope is 400 N. The car starts to accelerate steadily. If the tension in the rope is now 1650 N, with what acceleration is the trailer moving ?
(a) 1.75 ms–2
(b) 0.75 ms–2
(c) 2.5 ms–2
(d) 1.25 ms–2

D

Question. Block A is moving with acceleration A along a frictionless horizontal surface. When a second block, B is placed on top of Block A the acceleration of the combined blocks drops to 1/5 the original value. What is the ratio of the mass of A to the mass of B?
(a) 5 : 1
(b) 1 : 4
(c) 3 : 1
(d) 2 : 1

B

Question. A rifle man, who together with his rifle has a mass of 100 kg, stands on a smooth surface and fires 10 shots horizontally.  Each bullet has a mass 10 g and a muzzle velocity of 800 ms–1. The velocity which the rifle man attains after firing 10 shots is
(a) 8 ms-1
(b) 0.8 ms-1
(c) 0.08ms-1
(d) – 0.8 ms-1

B

Question. A block of mass 4 kg rests on an inclined plane. The inclination to the plane is gradually increased. It is found that when the inclination is 3 in 5, the block just begins to slidedown the plane. The coefficient of friction between the block and the plane is
(a) 0.4
(b) 0.6
(c) 0.8
(d) 0.75.

D

Question. The minimum velocity (in ms-1) with which a car driver must traverse a flat curve of radius 150 m and coefficient of friction 0.6 to avoid skidding is
(a) 60
(b) 30
(c) 15
(d) 25

B

Question. A body of mass 2 kg is placed on a horizontal surface having kinetic friction 0.4 and static friction 0.5. If the force applied on the body is 2.5 N, then the frictional force acting on the body will be [g = 10 ms–2]
(a) 8 N
(b) 10 N
(c) 20 N
(d) 2.5 N

D

Question. A ball of mass 0.5 kg moving with a velocity of 2 m/sec strikes a wall normally and bounces back with the same speed. If the time of contact between the ball and the wall is one millisecond, the average force exerted by the wall on the ball is :
(a) 2000 newton
(b) 1000 newton
(c) 5000 newton
(d) 125 newton

A

Question. The mass of the lift is 100 kg which is hanging on the string.
The tension in the string, when the lift is moving with constant velocity, is (g = 9.8 m/sec2)
(a) 100 newton
(b) 980 newton
(c) 1000 newton
(d) None of these

B

Question. A 5000 kg rocket is set for vertical firing. The exhaust speed is 800 m/s. To give an initial upward acceleration of 20 m/s2, the amount of gas ejected per second to supply the needed thrust will be (Take g = 10 m/s2)
(a) 127.5 kg/s
(b) 137.5 kg/s
(c) 155.5 kg/s
(d) 187.5 kg/s

D

Question. A bullet is fired from a gun. The force on the bullet is given by F = 600 – 2 × 105 t
Where, F is in newtons and t in seconds. The force on the bullet becomes zero as soon as it leaves the barrel. What is the average impulse imparted to the bullet?
(a) 1.8 N-s
(b) Zero
(c) 9 N-s
(d) 0.9 N-s