# MCQs for Physics Class 11 with Answers Chapter 5 Laws of Motion

Students of class 11 Physics should refer to MCQ Questions Class 11 Physics Laws of Motion with answers provided here which is an important chapter in Class 11 Physics NCERT textbook. These MCQ for Class 11 Physics with Answers have been prepared based on the latest CBSE and NCERT syllabus and examination guidelines for Class 11 Physics. The following MCQs can help you to practice and get better marks in the upcoming class 11 Physics examination

## Chapter 5 Laws of Motion MCQ with Answers Class 11 Physics

Question. A metre scale is moving with uniform velocity. This implies
(a) the force acting on the scale is zero, but a torque about the centre of mass can act on the scale
(b) the force acting on the scale is zero and the torque acting about centre of mass of the scale is also zero
(c) the total force acting on it need not be zero but the torque on it is zero
(d) neither the force nor the torque need to be zero

B

Question. A car of mass m starts from rest and acquires a velocity along east, vr = viˆ (v > 0) in two seconds. Assuming the car moves with uniform acceleration, the force exerted on the car is
(a) mv/2 eastward and is exerted by the car engine
(b) mv/2 eastward and is due to the friction on the tyres exerted by the road
(c) more than mv/2 eastward exerted due to the engine and overcomes the friction of the road
(d) mv/2 exerted by the engine

B

Question. A cricket ball of mass 150 g has an initial velocity ur = (3iˆ + 4 ˆj)ms-1 and a final velocity vr = -(3iˆ + 4 ˆj)ms-1 , after being hit. The change in momentum (final momentuminitial momentum) is (in kgms–1)
(a) zero
(b) -(0.45iˆ + 0.6 ˆj)
(c) -(0.9 ˆj +1.2 ˆj)
(d) -5(iˆ + ˆj)iˆ

C

Question. A hockey player is moving northward and suddenly turns westward with the same speed to avoid an opponent. The force that acts on the player is
(a) frictional force along westward
(b) muscle force along southward
(c) frictional force along sotuh-west
(d) muscle force along south-west

C

Question. A ball is travelling with uniform translatory motion. This means that
(a) it is at rest
(b) the path can be a straight line or circular and the ball travels with uniform speed
(c) all parts of the ball have the same velocity (magnitude and direction) and the velocity is constant
(d) the centre of the ball moves with constant velocity and the ball spins about its centre uniformly

C

Question. A body of mass 2 kg travels according to the law x(t) = pt + qt2 + rt3 where, q = 4 ms–2, p = 3 ms–1 and r = 5 ms–3. The force acting on the body at t = 2s is
(a) 136 N
(b) 134 N
(c) 158 N
(d) 68 N

A

Question. Three blocks with masses m, 2 m and 3 m are connected by strings as shown in the figure. After an upward force F is applied on block m, the masses move upward at constant speed v. What is the net force on the block of mass 2m? (g is the acceleration due to gravity)

(a) 2 mg
(b) 3 mg
(c) 6 mg
(d) zero

D

Question. A system consists of three masses m1, m2 and m3 connected by a string passing over a pulley P. The mass m1 hangs freely and m2 and m3 are on a rough horizontal table (the coefficient of friction = μ). The pulley is frictionless and of negligible mass. The downward acceleration of mass m1 is : (Assume m1 = m2 = m3 = m)

C

Question. A car is moving in a circular horizontal track of radius 10 m with a constant speed of 10 m/s. A bob is suspended from the roof of the car by a light wire of length 1.0 m. The angle made by the wire with the vertical is
(a) 0°
(b) π/3
(c) π/6
(d) π/4

D

Question. The force ‘F’ acting on a particle of mass ‘m’ is indicated by the force-time graph shown below. The change in momentum of the particle over the time interval from zero to 8 s is :

(a) 24 Ns
(b) 20 Ns
(c) 12 Ns
(d) 6 Ns

C

Question. A body with mass 5 kg is acted upon by a force F = (-3iˆ + 4 ˆj) N. If its initial velocity at t = 0 is v = (6iˆ -12 ˆj) ms-1 , the time at which it will just have a velocity along the y-axis is
(a) never
(b) 10 s
(c) 2 s
(d) 15 s

B

Question. In the previous problem (3), the magnitude of the momentum transferred during the hit is
(a) zero
(b) 0.75 kg-m s–1
(c) 1.5 kg-m s–1
(d) 1.4 kg-m s–1

C

Question. Conservation of momentum in a collision between particles can be understood from
(a) Conservation of energy
(b) Newton’s first law only
(c) Newton’s second law only
(d) both Newton’s second and third law

D

Question. Three blocks A, B and C of masses 4 kg, 2 kg and 1 kg respectively, are in contact on a frictionless surface, as shown. If a force of 14 N is applied on the 4 kg block then the contact force between A and B is

(a) 6 N
(b) 8 N
(c) 18 N
(d) 2 N

A

Question. A balloon with mass ‘m’ is descending down with an acceleration ‘a’ (where a < g). How much mass should be removed from it so that it starts moving up with an acceleration ‘a’?

A

Question. A block A of mass m1 rests on a horizontal table. A light string connected to it passes over a frictionless pulley at the edge of table and from its other end another block B of mass m2 is suspended. The coefficient of kinetic friction between the block and the table is μk. When the block A is sliding on the table, the tension in the string is

B

Question. Two blocks A and B of masses 3 m and m respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of A and B immediately after the string is cut, are respectively :

A

Question. A plank with a box on it at one end is gradually raised about the other end. As the angle of inclination with the horizontal reaches 30º the box starts to slip and slides 4.0 m down the plank in 4.0s. The coefficients of static and kinetic friction between the box and the plank will be, respectively :

(a) 0.6 and 0.5
(b) 0.5 and 0.6
(c) 0.4 and 0.3
(d) 0.6 and 0.6

A

Question. What is the minimum velocity with which a body of mass m must enter a vertical loop of radius R so that it can complete the loop ?
(a) √gR
(b) √2gR
(c) √3gR
(d) √5gR

D

Question. Two stones of masses m and 2 m are whirled in horizontal circles, the heavier one in radius r/2 and the lighter one in radius r. The tangential speed of lighter stone is n times that of the value of heavier stone when they experience same centripetal forces. The value of n is :
(a) 3
(b) 4
(c) 1
(d) 2

D

Question. One end of string of length l is connected to a particle of mass ‘m’ and the other end is connected to a small peg on a smooth horizontal table. If the particle moves in circle with speed ‘v’ the net force on the particle (directed towards centre) will be (T represents the tension in the string)

D

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 constant force F = m2g/2 is applied on the block of mass m1 as shown in fig. The string and the pulley are light and the surface of the table is smooth. The acceleration of m1 is

A

Question. A body of mass 0.4kg starting at origin at t = 0 with a speed of I0 m is in the positive x-axis direction is subjected to a constant force F = 8N towards negative x-axis. Calculate the position of the particle after 25 s.
(a) – 6000 m
(b) – 8000 m
(c) 4000 m
(d) 7000 m

A

Question. A ball of mass 0.4 kg thrown up in air with velocity 30 ms-1 reaches the highest point in 2.5 second . The air resistance encountered by the ball during upward motion is
(a) 0.88 N
(b) 8800N
(c) 300 dyne
(d) 300 N.

A

Question. A rectangular block is placed on a rough horizontal surface in two different ways as shown, then

(a) friction will be more in case (a)
(b) friction will be more in case (b)
(c) friction will be equal in both the cases
(d) friction depends on the relations among its dimensions.

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. 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. A 10 kg stone is suspended with a rope of breaking strength 30 kg-wt. The minimum time in which the stone can be raised through a height 10 m starting from rest is (Take g = 10N/ kg)
(a) 0.5 s
(b) 1.0 s
(c) √2 / 3 s
(d) 2 s

B

Question. For the arrangement shown in the Figure the tension in the string is [Given : tan-1 (0.8) = 39° ]

(a) 6 N
(b) 6.4 N
(c) 0.4 N
(d) zero.

D

Question. A 1 kg block and a 0.5 kg block move together on a horizontal frictionless surface . Each block exerts a force of 6 N on the other. The block move with a uniform acceleration of

(a) 3ms-2
(b) 6ms-2
(c) 9 ms-2
(d) 12 ms-2

D

Question. A player caught a cricket ball of mass 150 g moving at a rate of 20 m/s. If the catching process is completed in 0.1s, the force of the blow exerted by the ball on the hand of the player is equal to
(a) 150 N
(b) 3 N
(c) 30 N
(d) 300 N

C

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. 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 conveyor belt is moving at a constant speed of 2m/s. A box is gently dropped on it. The coefficient of friction between them is μ = 0.5. The distance that the box will move relative to belt before coming to rest on it taking g = 10 ms–2, is
(a) 1.2 m
(b) 0.6 m
(c) zero
(d) 0.4 m

D

Question. A spring of force constant k is cut into two pieces whose lengths are in the ratio 1 : 2. What is the force constant of the longer piece ?
(a) k/2
(b) 3k/2
(c) 2 k
(d) 3k

B

Question. A block of mass m is resting on a smooth horizontal surface. One end of a uniform, rope of mass ml 3 is fixed to the block, which is pulled in the horizontal direction by applying force F at the other end. The tension in the middle of the rope is

E

Question. A bridge is in the from of a semi-circle of radius 40m. The greatest speed with which a motor cycle can cross the bridge without leaving the ground at the highest point is (g = 10 m s–2) (frictional force is negligibly small)
(a) 40 m s–1
(b) 20 m s–1
(c) 30 m s–1
(d) 15 m s–1

B

Question. A motor cycle is going on an overbridge of radius R. The driver maintains a constant speed. As the motor cycle is ascending on the overbridge, the normal force on it
(a) increases
(b) decreases
(c) remains the same
(d) fluctuates erratically

A

Question. A body of mass 5 kg explodes at rest into three fragments with masses in the ratio 1 : 1 : 3. The fragments with equal masses fly in mutually perpendicular directions with speeds of 21 m/s. The velocity of heaviest fragment in m/s will be
(a) 7√2
(b) 5√2
(c) 3√2
(d) 2

A

Question. A body of mass M hits normally a rigid wall with velocity V and bounces back with the same velocity. The impulse experienced by the body is
(a) MV
(b) 1.5 MV
(c) 2 MV
(d) zero

C

Question. A bus moving on a level road with a velocity v can be stopped at a distance of x, by the application of a retarding force F. The load on the bus is increased by 25% by boarding the passengers. Now, if the bus is moving with the same speed and if the same retarding force is applied, the distance travelled by the bus before it stops is
(a) I.25x
(b) x
(c) 5x
(d) 2.5x

A

Question. Consider a car moving on a straight road with a speed of 100 m/s . The distance at which car can be stopped is [μk = 0.5]
(a) 1000 m
(b) 800 m
(c) 400 m
(d) 100 m

A

Question. The upper half of an inclined plane with inclination Φ is perfectly smooth while the lower half is rough. A body starting from rest at the top will again come to rest at the bottom if the coefficient of friction for the lower half is given by
(a) 2 cos Φ
(b) 2 sin Φ
(c) tan Φ
(d) 2 tan Φ

D

Question. A block of mass m is placed on a smooth wedge of inclination q. The whole system is accelerated horizontally so that the block does not slip on the wedge. The force exerted by the wedge on the block (g is acceleration due to gravity) will be
(a) mg/cos θ
(b) mg cos θ
(c) mg sin θ
(d) mg

A

Question. Two bodies of masses m and 4m are moving with equal kinetic energies. The ratio of their linear momenta will be
(a) 1 : 4
(b) 4 : 1
(c) 1 : 2
(d) 2 : 1

C

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 constant retarding force of 80 N is applied to a body of mass 50 kg which is moving initially with a speed of 20m/s. What would be the tin1e required by the body to come to rest?
(a) 15 s
(c) 12.5 s
(b) 14 s
(d) 18 s

C

Question. A 1 0 kg stone is suspended with a rope of breaking strength 30 kg-wt. The minimum tin1e in which the stone can be raised through a height 10 m starting from rest is (taking, g= l0 N kg-1)

B

Question. The bus moving with a speed of 42 km/h is brought to a A stop by brakes after 6 m. If the same bus is moving at a speed of 90 km/h, then the minimum stopping distance is
(a) 15.48 m
(b) l8.64 m
(c) 22.13 m
(d) 27.55 m