# MCQ Chapter 5 Laws of Motion Class 11 Physics

Please refer to Laws of Motion MCQ Questions Class 11 Physics below. These MCQ questions for Class 11 Physics with answers have been designed as per the latest NCERT, CBSE books, and syllabus issued for the current academic year. These objective questions for Laws of Motion will help you to prepare for the exams and get more marks.

## Laws of Motion MCQ Questions Class 11 Physics

Please see solved MCQ Questions for Laws of Motion in Class 11 Physics. All questions and answers have been prepared by expert faculty of standard 11 based on the latest examination guidelines.

### MCQ Questions Class 11 Physics Laws of Motion

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. 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. A body of mass 1 kg moving with a uniform velocity of 1 ms-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) 10 N

A

Question. An object is resting at the bottom of two strings which are inclined at an angle of 120° with each other. Each string can withstand a tension of 20N. The maximum weight of the object that can be supported without breaking the string is
(a) 5 N
(b) 10 N
(c) 20 N
(d) 40 N

C

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 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) 0.08 ms-1
(d) – 0.8 ms-1

B

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

D

Question. A bag of sand of mass m is suspended by a rope. A bullet of mass m/20 is fired at it with a velocity v and gets embedded into it. The velocity of the bag finally is

D

Question. A body of mass 1.0 kg is falling with an acceleration of 10 m/ sec2. Its apparent weight will be (g = 10 m/sec2)
(a) 1.0 kg wt
(b) 2.0 kg wt
(c) 0.5 kg wt
(d) zero

D

Question. A horizontal force F is applied on back of mass m placed on a rough inclined plane of inclination θ . The normal reaction N is

(a) mg cos θ
(b) mg sin θ
(c) mg cos θ- F cos θ
(d) mg cos θ + F sin θ

D

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 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. In the question , the tension in the strings, when the lift is accelerating up with an acceleration 1 m/sec2, is
(a) 100 newton
(b) 980 newton
(c) 1080 newton
(d) 880 newton

C

Question. A solid sphere of 2 kg is suspended from a horizontal beam by two supporting wires as shown in fig. Tension in each wire is approximately (g = 10 ms–2)
(a) 30 N
(b) 20 N
(c) 10 N
(d) 5 N

B

Question. A force time graph for the motion of a body is shown in Fig. Change in linear momentum between 0 and 8s is

(a) zero
(b) 4 N-s
(c) 8 Ns
(d) None of these

A

Question. A person with his hand in his pocket is skating on ice at the rate of 10m/s and describes a circle of radius 50 m. What is his inclination to vertical : (g = 10 m/sec2)
(a) tan–1 (½)
(b) tan–1 (1/5)
(c) tan–1 (3/5)
(d) tan–1 (1/10)

B

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. 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. A block of mass 5 kg resting on a horizontal surface is connected by a cord, passing over a light frictionless pulley to a hanging block of mass 5 kg. The coefficient of kinetic friction between the block and the surface is 0.5. Tension in the cord is : (g = 9.8 m/sec2)

(a) 49 N
(b) Zero
(c) 36.75 N
(d) 2.45 N

C

Question. A cane filled with water is revolved in a vertical circle of radius 4 meter and the water just does not fall down. The time period of revolution will be
(a) 1 sec
(b) 10 sec
(c) 8 sec
(d) 4 sec

D

Question. A force F = 8 iˆ– 6jˆ – 10k newton produces an acceleration of 1 ms–2 in a body. The mass of the body is
(a) 10 kg
(b) 10√2 kg
(c) 10√3 kg
(d) 200 kg

B

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 m is moving with velocity v1, it is given an impulse such that the velocity becomes v2. Then magnitude of impulse is equal to
(a) m (v2 – v1)
(b) m (v1 – v )
(c) m x (v2 – v1)
(d) 0.5m (v2 – v1 )

A

Question. The coefficient of friction between the rubber tyres and the road way is 0.25. The maximum speed with which a car can be driven round a curve of radius 20 m without skidding is (g = 9.8 m/s2)
(a) 5 m/s
(b) 7 m/s
(c) 10 m/s
(d) 14 m/s

B

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. 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 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 slide down 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. 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 20 m 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. When the road is dry and the coefficient of the friction is m, the maximum speed of a car in a circular path is 10 ms–1. If the road becomes wet and μ = μ /2 what is the maximum speed permitted?
(a) 5 ms–1
(b) 10 ms–1
(c) 10√2 ms-1
(d) 5√2 ms-1

D

Question. A heavy uniform chain lies on horizontal table top. If the coefficient of friction between the chain and the table surface is 0.25, then the maximum fraction of the length of the chain that can hang over one edge of the table is
(a) 20%
(b) 25%
(c) 35%
(d) 15%

A

Question. Two pulley arrangements of figure given are identical. The mass of the rope is negligible. In fig (a), the mass m is lifted by attaching a mass 2m to the other end of the rope. In fig (b), m is lifted up by pulling the other end of the rope with a constant downward force F = 2mg. The acceleration of m in the two cases are respectively

(a) 3g, g
(b) g /3, g
(c) g /3, 2g
(d) g, g /3

B

Question. Three blocks of masses m1, m2 and m3 are connected by massless strings, as shown, on a frictionless table. They are pulled with a force T3 = 40 N. If m1 = 10 kg, m2 = 6 kg and m3 = 4kg, the tension T2 will be

(a) 20 N
(b) 40 N
(c) 10 N
(d) 32 N

D

Question. A ball of mass 400 gm is dropped from a height of 5 m. A boy on the ground hits the ball vertically upwards with a bat with an average force of 100 newton so that it attains a vertical height of 20 m. The time for which the ball remains in contact with the bat is (g = 10 m/s2)
(a) 0.12 s
(b) 0.08 s
(c) 0.04 s
(d) 12 s

A

Question. The linear momentum p of a body moving in one dimension varies with time according to the equating P = a + bt2 where a and b are positive constants. The net force acting on the body is
(a) proportional to t2
(b) a constant
(c) proportional to t
(d) inversely proportional to t

C

Question. Block A of weight 100 kg rests on a block B and is tied with horizontal string to the wall at C. Block B is of 200 kg. The coefficient of friction between A and B is 0.25 and that between B and surface is 1/3 The horizontal force F
necessary to move the block B should be (g = 10 m/s2)

(a) 1050 N
(b) 1450 N
(c) 1050 N
(d) 1250 N

D

Question. A ball mass m falls vertically to the ground from a height h1 and rebounds to a height h2. The change in momentum of the ball of striking the ground is

D

Question. In the given figure, the pulley is assumed massless and frictionless. If the friction force on the object of mass m is f, then its acceleration in terms of the force F will be equal to

B

Question. An open topped rail road car of mass M has an initial velocity v0 along a straight horizontal frictionless track. It suddenly starts raising at time t = 0. The rain drops fall vertically with velocity u and add a mass m kg/sec of water. The velocity of car after t second will be (assuming that it is not completely filled with water)

B

Question. A particle of mass 0.3 kg subject to a force F = – kx with k = 15 N/m . What will be its initial acceleration if it is released from a point 20 cm away from the origin ?
(a) 15 m/s2
(b) 3 m/s2
(c) 10 m/s2
(d) 5 m/s2

C

Question. A bullet of mass m is fired from a gun of mass M. The recoiling gun compresses a spring of force constant k by a distance d. Then the velocity of the bullet is

C

Question. A block is kept on a frictionless inclined surface with angle of inclination ‘ a ’ . The incline is given an acceleration ‘a’ to keep the block stationary. Then a is equal to

(a) g cosec α
(b) g / tan α
(c) g tan α
(d) g

C

Question. A smooth block is released at rest on a 45° incline and then slides a distance ‘d’. The time taken to slide is ‘n’ times as much to slide on rough incline than on a smooth incline. The coefficient of friction is

B

Question. The coefficient of static friction, μs, between block A of mass 2 kg and the table as shown in the figure is 0.2. What would be the maximum mass value of block B so that the two blocks do not move? The string and the pulley are assumed to be smooth and massless. (g = 10 m/s2)

(a) 0.4 kg
(b) 2.0 kg
(c) 4.0 kg
(d) 0.2 kg

A

Question. A body under the action of a force F = 6ˆi – 8ˆj+10kˆ, acquires an acceleration of 1 m/s2. The mass of this body must be
(a) 10 kg
(b) 20 kg
(c) 10√2 kg
(d) 2√10 kg

C

Question. A round uniform body of radius R, mass M and moment of inertia I rolls down (without slipping) an inclined plane making an angle θ with the horizontal. Then its acceleration is

B

Question. The upper half of an inclined plane of inclination θ is perfectly smooth while lower half is rough. A block starting from rest at the top of the plane will again come to rest at the bottom, if the coefficient of friction between the block and lower half of the plane is given by

B

Question. An explosion breaks a rock into three parts in a horizontal plane. Two of them go off at right angles to each other. The first part of mass 1 kg moves with a speed of 12 ms–1 and the second part of mass 2 kg moves with speed 8 ms–1. If the third part flies off with speed 4 ms–1 then its mass is
(a) 5 kg
(b) 7 kg
(c) 17 kg
(d) 3 kg

A

Question. A person of mass 60 kg is inside a lift of mass 940 kg and presses the button on control panel. The lift starts moving upwards with an acceleration 1.0 m/s2. If g = 10 ms–2, the tension in the supporting cable is
(a) 8600 N
(b) 9680 N
(c) 11000 N
(d) 1200 N