# MCQ Chapter 6 Work Energy and Power Class 11 Physics

Please refer to Work Energy and Power 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 Work Energy and Power will help you to prepare for the exams and get more marks.

## Work Energy and Power MCQ Questions Class 11 Physics

Please see solved MCQ Questions for Work Energy and Power 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 Work Energy and Power

Question. A nucleus ruptures into two nuclear parts which have their velocity ratio equal to 2 :1. The ratio of their respective nuclear sizes (nuclear radii )is
(a) 1 : 2
(b) 1: 2
(c) 1 : 21/3
(d) 1 : 8

C

Question. A metallic wire of length L metre extends by l metre when stretched by suspending a weight Mg from it. The mechanical energy stored in the wire is

C

Question. A body of mass m accelerates uniformly from rest to v1 in time t1. As a function of t, the instantaneous power delivered to the body is

D

Question. A one-ton car moves with a constant velocity of 15 ms–1 on a rough horizontal road. The total resistance to the motion of the car is 12% of the weight of the car. The power required to keep the car moving with the same constant velocity of 15ms–1 is [Take g = 10 ms–2]
(a) 9 kW
(b) 18 kW
(c) 24 kW
(d) 36 kW

B

Question. A body starts from rest and acquires a velocity V in time T. The work done on the body in time t will be proportional to

D

Question. A ball is allowed to fall from a height of 10 m. If there is 40% loss of energy due to impact, then after one impact ball will go up to
(a) 10 m
(b) 8 m
(c) 4 m
(d) 6 m

D

Question. Hail storms are observed to strike the surface of the frozen lake at 300 with the vertical and rebound at 600 with the vertical. Assume contact to be smooth, the coefficient of restitution is

B

Question. The bob A of a simple pendulum is released when the string makes an angle of 45º with the vertical. It hits another bob B of the same material and same mass kept at rest on the table. If the collision is elastic

(a) both A and B rise to the same height
(b) both A and B come to rest at B
(c) both A and B move with the velocity of A
(d) A comes to rest and B moves with the velocity of A

D

Question. Two inclined frictionless tracks, one gradual and the other steep meet at A from where two stones are allowed to slide down from rest, one on each track as shown in figure. Which of the following statement is correct?

(a) Both the stones reach the bottom at the same time but not with the same speed
(b) Both the stones reach the bottom with the same speed and stone I reaches the bottom earlier than stone II
(c) Both the stones reach the bottom with the same speed and stone II reaches the bottom earlier than stone I
(d) Both the stones reach the bottom at different times and with different speeds

C

Question. Two masses ma and mb moving with velocities va and vb in opposite direction collide elastically and after the collision ma and mb move with velocities Vb and Va respectively. Then the ratio ma/mb is

C

Question. A particle moves in a straight line with retardation proportional to its displacement. Its loss of kinetic energy for any displacement x is proportional to
(a) x
(b) ex
(c) x2
(d) loge x

C

Question. A mass m is moving with velocity v collides inelastically with a bob of simple pendulum of mass m and gets embedded into it. The total height to which the masses will rise after collision is

A

Question. A raindrop falling from a height h above ground, attains a near terminal velocity when it has fallen through a height (3/4)h. Which of the diagrams shown in figure correctly shows the change in kinetic and potential energy of the drop during its fall up to the ground?

B

Question. In a shotput event an athlete throws the shotput of mass 10 kg with an initial speed of 1 m s–1 at 45° from a height 1.5 m above ground. Assuming air resistance to be negligible and acceleration due to gravity to be 10 m s–2, the kinetic energy of the shotput when it just reaches the ground will be
(a) 2.5 J
(b) 5.0 J
(c) 52.5 J
(d) 155.0 J

D

Question. A motor drives a body along a straight line with a constant force. The power P developed by the motor must vary with time t according to

D

Question. The kinetic energy of particle moving along a circle of radius R depends upon the distance covered S and is given by K = aS where a is a constant. Then the force acting on the particle is
(a) aS
(b) 2(aS)2/R
(c) aS2/R2
(d) 2aS/2

D

Question. A weight suspended from the free end of a vertically hanging spring produces an extension of 3 cm. The spring is cut into two parts so that the length of the longer part is 2/3 of the original length, If the same weight is now suspended from the longer part of the spring, the extension produced will be
(a) 0.1 cm
(b) 0.5 cm
(c) 1 cm
(d) 2 cm

D

Question. A 10 m long iron chain of linear mass density 0.8 kg m–1 is hanging freely from a rigid support. If g = 10 ms–2, then the power required to left the chain upto the point of support in 10 second
(a) 10 W
(b) 20W
(c) 30 W
(d) 40 W

D

Question. A ramp is constructed in parabolic shape such that the height y of any point on its surface is given in terms of the point’s horizontal distance x from the bottom of the ramp be y = x2/2L. A block of granite is to be set on the ramp; the coefficient of static friction is 0.80. What is the maximum x, coordinate at which the block can be placed on the ramp and remain at rest, if L = 10 m?

(a) 8 m
(b) 8.4 m
(c) 9 m
(d) 9.4 m

A

Question. n small balls each of mass m impinge elastically each second on a surface with velocity v. The force experienced by the surface will be
(a) 1/2mnv
(b) 2 mnv
(c) mnv
(d) 2 mnv

C

Question. Which of the diagrams shown in figure most closely shows the variation in kinetic energy of the earth as it moves once around the sun in its elliptical orbit?

D

Question. A cricket ball of mass 150 g moving with a speed of 126 km/ h hits at the middle of the bat, held firmly at its position by the batsman. The ball moves straight back to the bowler after hitting the bat. Assuming that collision between ball and bat is completely elastic and the two remain in contact for 0.001s, the force that the batsman had to apply to hold the bat firmly at its place would be
(a) 10.5 N
(b) 21 N
(c) 1.05 × 104 N
(d) 2.1 × 104 N

C

Question. A horse drinks water from a cubical container of side 1 m. The level of the stomach of horse is at 2 m from the ground. Assume that all the water drunk by the horse is at a level of 2m from the ground. Then minimum work done by the horse in drinking the entire water of the container is (Take Pwater = 1000 kg/m3 and g = 10 m/s2 ) –

(a) 10 kJ
(b) 15 kJ
(c) 20 kJ
(d) zero

D

Question. The ball rolls down without slipping (which is at rest at a) along ab having friction. It rolls to a maximum height hc where bc has no friction. Ka, Kb and Kc are kinetic energies at a, b and c. Which of the following is correct ?

(a) Ka = Kc, ha = hc
(b) Kb > Kc, ha = hc
(c) Kb > Kc, ha < hc
(d) Kb > Kc, ha > hc

D

Question. A body falls freely under gravity. Its velocity is v when it has lost potential energy equal to U. What is the mass of the body ?
(a) U2/v2
(b) 2U2/v2
(c) 2U/v2
(d) U /v2

C

Question. An electron and a proton are moving under the influence of mutual forces. In calculating the change in the kinetic energy of the system during motion, one ignores the magnetic force of one on another. This is, because
(a) the two magnetic forces are equal and opposite, so they produce no net effect
(b) the magnetic forces do not work on each particle
(c) the magnetic forces do equal and opposite (but nonzero) work on each particle
(d) the magnetic forces are necessarily negligible

B

Question. If v be the instantaneous velocity of the body dropped from the top of a tower, when it is located at height h, then which of the following remains constant ?

B

Question. The coefficient of friction between the tyres and the road is μ. A car is moving with momentum p. What will be the stopping distance due to friction alone ? The mass of the car is m.
(a) p2/2mg
(b) p2/2mmg
(c) p2/2m2mg
(d) p2/2mg

C

Question. A particle of mass 10 kg moving eastwards with a speed 5 ms–1 collides with another particle of the same mass moving north-wards with the same speed 5 ms–1. The two particles coalesce on collision. The new particle of mass 20 kg will move in the north-east direction with velocity
(a) 10 ms–1
(b) 5 ms–1
(c) (5 / √2)ms-1
(d) none of these

C

Question. A person holding a rifle (mass of person and rifle together is 100 kg) stands on a smooth surface and fires 10 shots horizontally, in 5 s. Each bullet has a mass of 10 g with a muzzle velocity of 800 ms–1. The final velocity acquired by the person and the average force exerted on the person are
(a) –1.6 ms–1; 8 N
(b) –0.08 ms–1; 16 N
(c) – 0.8 ms–1; 8 N
(d) –1.6 ms–1; 16 N

C

Question. A metal ball of mass 2 kg moving with a velocity of 36 km/h has a head on collision with a stationary ball of mass 3 kg. If after the collision, the two balls move together, the loss in kinetic energy due to collision is
(a) 140 J
(b) 100 J
(c) 60 J
(d) 40 J

C

Question. A rubber ball is dropped from a height of 5m on a plane, where the acceleration due to gravity is not shown. On bouncing it rises to 1.8 m. The ball loses its velocity on bouncing by a factor of
(a) 16/25
(b) 2/5
(c) 3/5
(d) 9/25

B

Question. A body of mass (4m) is lying in x-y plane at rest. It suddenly explodes into three pieces. Two pieces, each of mass (m) move perpendicular to each other with equal speeds (v). The total kinetic energy generated due to explosion is :
(a) mv2
(b) (3/2) mv2
(c) 2 mv2
(d) 4 mv2

B

Question. A 3 kg ball strikes a heavy rigid wall with a speed of 10 m/ s at an angle of 60º. It gets reflected with the same speed and angle as shown here. If the ball is in contact with the wall for 0.20s, what is the average force exerted on the ball by the wall?

(a) 150 N
(b) Zero
(c) 150√3N
(d) 300 N

C

Question. In a simple pendulum of length l the bob is pulled aside from its equilibrium position through an angle q and then released. The bob passes through the equilibrium position with speed

D

Question. Two similar springs P and Q have spring constants KP and KQ, such that KP > KQ. They are stretched, first by the same amount (case a,) then by the same force (case b). The work done by the springs WP and WQ are related as, in case (a) and case (b), respectively
(a) WP = WQ ; WP = WQ
(b) WP > WQ ; WQ > WP
(c) WP < WQ ; WQ < WP
(d) WP = WQ ; WP > WQ

B

Question. A stationary particle explodes into two particles of masses m1 and m2 which move in opposite directions with velocities v1 and v2. The ratio of their kinetic energies E1/E2 is
(a) m1v2/m2v1
(b) m2/m1
(c) m1/m2
(d) 1

B

Question. A ball moving with velocity 2 m/s collides head on with another stationary ball of double the mass. If the coefficient of restitution is 0.5, then their velocities (in m/s) after collision will be
(a) 0, 1
(b) 1, 1
(c) 1, 0.5
(d) 0, 2

A

Question. A mass m moving horizontally (along the x-axis) with velocity v collides and sticks to mass of 3m moving vertically upward (along the y-axis) with velocity 2v. The final velocity of the combination is

A

Question. The potential energy of particle in a force field is U = A/r2 – B/r, where A and B are positive constants and r is the distance of particle from the centre of the field. For stable equilibrium, the distance of the particle is
(a) B / 2A
(b) 2A / B
(c) A / B
(d) B / A

B

Question. If the kinetic energy of a body is increased by 300%, the momentum of the body is increased by
(a) 300%
(b) 200%
(c) 100%
(d) 50%

C

Question. A particle of mass 10 g moves along a circle of radius 6.4 cm with a constant tangential acceleration. What is the magnitude of this acceleration if the kinetic energy of the particle becomes equal to 8 × 10–4 J by the end of the second revolution after the beginning of the motion ?
(a) 0.1 m/s2
(b) 0.15 m/s2
(c) 0.18 m/s2
(d) 0.2 m/s2

A

Question. Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m/s. Take ‘g’ constant with a value 10 m/s2. The work done by the (i) gravitational force and the (ii) resistive force of air is
(a) (i) 1.25 J (ii) –8.25 J
(b) (i) 100 J (ii) 8.75 J
(c) (i) 10 J (ii) – 8.75 J
(d) (i) – 10 J (ii) –8.25 J

C

Question. If the mass of the body is halved and velocity gets doubled then final kinetic energy would be ………of initial.
(a) same
(b) four times
(c) double
(d) eight times

C

Question. A train of weight 107 N is running on a level track with uniform speed of 36 km h–1. The frictional force is 0.5 kg per quintal. If g = 10 m/s2, then power of engine is
(a) 500 kW
(b) 50 kW
(c) 5 kW
(d) 0.5 kW

A

Question. A ball is thrown vertically downwards from a height of 20 m with an initial velocity v0. It collides with the ground loses 50 percent of its energy in collision and rebounds to the same height. The initial velocity v0 is :
(Take g = 10 ms–2)
(a) 20 ms–1
(b) 28 ms–1
(c) 10 ms–1
(d) 14 ms–1

A

Question. A bicyclist comes to a skidding stop in 10 m. During this process, the force on the bicycle due to the road is 200N and is directly opposed to the motion. The work done by the cycle on the road is
(a) + 2000 J
(b) – 200 J
(c) zero
(d) – 20,000 J

C

Question. A body is falling freely under the action of gravity alone in vaccum. Which of the following quantities remain constant during the fall?
(a) Kinetic energy
(b) Potential energy
(c) Total mechanical energy
(d) Total linear momentum

C

Question. On a frictionless surface a block of mass M moving at speed v collides elastically with another block of same mass M which is initially at rest. After collision the first block moves at an angle q to its initial direction and has a speed v/3. The second block’s speed after the collision is

D

Question. A particle of mass m moving eastward with a speed v collides with another particle of the same mass moving northwards with the same speed. If two particles coalesce on collision, the new particle of mass 2 m will move in the north-east direction with a velocity
(a) v / 2
(b) v 2
(c) v/ 2
(d) None of these

C

Question. A particle is moving in a region, where its potential energy U varies with co-ordinates x, y and z as  U = a/2 (x2 + y2 + z2) , where a is a positive constant. The force acting on the particle is
(a) − a(x𝑖̂ + y𝑗̂ + z𝑘̂)
(b) − 2a(x𝑖̂ + y𝑗̂ + z𝑘̂)
(c) − a/2 ( x2 + y2 + z2
(d) (x𝑖̂ + y𝑗̂ + z𝑘̂)

A

Question. A block of mass m is lowered vertically by a distance d with constant acceleration g/4 by means of a light inextensible string. Work done on the block by gravity is
(a) mgd/4
(b) 3mgd/4
(c) −3mgd/4
(d) mgd

D

Question. A body of mass m is lifted up from the earth surface to a height R above the earth’s surface without changing its kinetic energy. The work done in this process is equal to
(a) Zero by the resultant force acting on the body
(b) mgR/2 by the applied force acting on the body
(c) –mgR/2 by the gravitational force acting on the body
(d) All of these

D

Question. A knife having mass m is dropped from a height h above the surface of earth. If the knife penetrates upto distance x in the soil. The average force applied by the soil is
(a) mg(h/x + 1)
(b) mgh /x
(c) mg(h/x − 1)
(d) mgx/h

A

Question. The potential energy U of a diatomic molecule varies with interatomic separation r as U = a/r12 − b/r6 , where a and b are positive constants. Find the interatomic separation for which atoms are in equilibrium
(a) Zero
(b) (b/2a)1/6
(c) (2a/b)1/6
(d) (a/b)1/6

C

Question. A stone is tied to a string of length l and is moving in vertical circle such that the tension in the string at the highest position of stone is zero. Find the angle θ of string with lowest position when tension in the string is equal to the weight of stone

(a) cos−1(1/3)
(b) cos−1(2/3)
(c) cos−1(−2/3)
(d) sin−1(1/3)

C

Question. A body of mass (m) moving with speed v compresses a spring of spring constant(K). Maximum compression in spring is given by

B

Question. A ball of mass 500 gm moving with speed 2 m/s collide to a floor making an angle of 45° with vertical.
If coefficient of restitution is 1/√3 , then the angle made by the ball with normal, after collision is
(a) 60°
(b) 30°
(c) 45°
(d) 37°

B

Question. A body A of mass m elastically collides with another identical body B as shown in figure. The velocity of body A after collision is

(a) v̅
(b) v̅/2
(c) Zero
(d) v̅/3

C

QuestionA stationary body explodes into two pieces of masse 6 kg and 4 kg, which move in opposite directions. The ratio of their kinetic energies E1/E2 is
(a) 3/2
(b) 13/2
(c) 2/3
(d) 2/13

C

Question. A bomb at rest explodes into two fragments of masses 3 kg and 1 kg. The ratio of magnitude of velocities of the smaller and bigger fragment is
(a) 3
(b) 1
(c) 1/2
(d) 1/3

A

Question. A ball moving with velocity = 6 m/s perpendicular to a wall collides with it. Magnitude of change in velocity of ball the due to collision is (Assuming coefficient of restitution = 1/3 ).

(a) 2 m/s
(b) 6 m/s
(c) 9 m/s
(d) 8 m/s