# MCQs for Physics Class 11 with Answers Chapter 6 Work Energy and Power

Students of class 11 Physics should refer to MCQ Questions Class 11 Physics Work Energy and Power 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 6 Work Energy and Power MCQ with Answers Class 11 Physics

MCQ Questions Class 11 Physics Work Energy and Power provided below have been prepared by expert teachers of grade 11. These objective questions with solutions are expected to come in the upcoming Standard 11 examinations. Learn the below provided MCQ questions to get better marks in examinations.

Question. A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments; one in which the charged particle is also a proton and in another, a positron. In the same time t, the work done on the two moving charged particles is
(a) same as the same force law is involved in the two experiments
(b) less for the case of a positron, as the positron moves away more rapidly and the force on it weakens
(c) more for the case of a positron, as the positron moves away a larger distance
(d) same as the work done by charged particle on the stationary proton.

C

Question. A mass of 0.5 kg moving with a speed of 1.5 m/s on a horizontal smooth surface, collides with a nearly weightless spring of force constant k = 50 N/m. The maximum compression of the spring would be

(a) 0.5 m
(b) 0.15 m
(c) 0.12 m
(d) 1.5m

B

Question. A man squatting on the ground gets straight up and stand. The force of reaction of ground on the man during the process is
(a) constant and equal to mg in magnitude
(b) constant and greater than mg in magnitude
(c) variable but always greater than mg
(d) at first greater than mg and later becomes equal to mg

D

Question. During inelastic collision between two bodies, which of the following quantities always remain conserved?
(a) Total kinetic energy
(b) Total mechanical energy
(c) Total linear momentum
(d) Speed of each body

C

Question. A small block of mass m is kept on a rough inclined surface of inclination θ fixed in an elevator. The elevator goes up with a uniform velocity v and the block does not slide on the wedge. The work done by the force of friction on the block in time t as seen by the observer on the inclined p lane will be
(a) zero
(b) mgvt cos2 θ
(c) mgvt sin2 θ
(d) mgvt sin2 θ

A

Question. The potential energy function for a particle executing linear SHM is given by V(x) = 1/2 kx2 where k is the force
constant of the oscillator (Fig.). For k = 0.5 N/m, the graph of V(x) versus x is shown in the figure. A particle of total
energy E turns back when it reaches x = ±xm. If V and K indicate the PE and KE, respectively of the particle at x =
+xm, then which of the following is correct

(a) V = O, K = E
(b) V = E, K = O
(c) V < E, K = O
(d) V = O, K < E

B

Question. A shell is fired from a cannon with a velocity V at an angle q with the horizontal direction. At the highest point in its path, it explodes into two pieces of equal masses. One of the pieces retraces its path to the cannon. The speed of the other piece immediately after the explosion is
(a) 3 V cos θ
(b) 2 V cos θ
(c) 3/2 V cos θ
(d) V cos θ

A

Question. Two identical ball bearings in contact with each other and resting on a frictionless table are hit head-on by another ball bearing of the same mass moving initially with a speed v as shown in figure

If the collision is elastic, which of the following (figure) is a possible result after collision?

B

Question. A body of mass 0.5 kg travels in a straight line with velocity v = a x3/2 where a = 5 m–1/2s–1. The work done by the net force during its displacement from x = 0 to x = 2 m is
(a) 15 J
(b) 50 J
(c) 10 J
(d) 100 J

B

Question. A particle moves in the X–Y plane under the influence of a force F such that its instantaneous momentum is p = iˆ2cos t +ˆj2sin t . What is the angle between the force and instantaneous momentum ?
(a) 0°
(b) 45°
(c) 90°
(d) 180°

C

Question. A body is moving unidirectionally under the influence of a source of constant power supplying energy. Which of the diagrams shown in figure correctly shown the displacement time curve for its motion?

B

Question. A mass of 5 kg is moving along a circular path of radius 1 m. If the mass moves with 300 rev/min, its kinetic energy would be
(a) 250 π2
(b) 100 π2
(c) 5 π2
(d) 0

A

Question. The force F acting on a body moving in a circle of radius r is always perpendicular to the instantaneous velocity v. The work done by the force on the body in half rotation is
(a) Fv
(b) F·2π
(c) Fr
(d) 0

D

Question. A particle of mass m1moving with velocity v strikes with a mass m2 at rest, then the condition for maximum transfer of kinetic energy is
(a) m1 >> m2
(b) m2 >> m2
(c) m1 = m2
(d) m1 = 2m2

C

Question. Two blocks of masses 10 kg and 4 kg are connected by a spring of negligible mass and placed on a frictionless horizontal surface. An impulse gives a velocity of 14 m/s to the heavier block in the direction of the lighter block. The velocity of the centre of mass is
(a) 30 m/s
(b) 20 m/s
(c) 10 m/s
(d) 5 m/s

C

Question. The negative of the distance rate of change of potential energy is equal to
(a) force acting on the particle in the direction of displacement
(b) acceleration of the particle, perpendicular to displacement
(c) power
(d) impulse.

A

Question. Which of the diagrams in figure correctly shows the change in kinetic energy of an iron sphere falling freely in a lake having sufficient depth to impart it a terminal velocity?

B

Question. A uniform force of (3iˆ+ ˆj) newton acts on a particle of mass 2 kg. The particle is displaced from position (2ˆi + kˆ) meter to position (4ˆi + 3ˆj – kˆ) meter. The work done by the force on the particle is
(a) 6 J
(b) 13 J
(c) 15 J
(d) 9 J

D

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 smooth sphere of mass M moving with velocity u directly collides elastically with another sphere of mass m at rest. After collision, their final velocities are V and v respectively. The value of v is

C

Question. A particle with total energy E is moving in a potential energy region U(x). Motion of the particle is restricted to the region when
(a) U(x) > E
(b) U(x) < E
(c) U(x) = O
(d) U(x) < E

D

Question. A force acts on a 30 gm particle in such a way that the position of the particle as a function of time is given by x = 3t – 4t2 + t3, where x is in metres and t is in seconds. The work done during the first 4 seconds is
(a) 576 mJ
(b) 450 mJ
(c) 490 mJ
(d) 530 mJ

A

Question. One coolie takes 1 minute to raise a suitcase through a height of 2 m but the second coolie takes 30 s to raise the same suitcase to the same height. The powers of two coolies are in the ratio of
(a) 1 : 2
(b) 1 : 3
(c) 2 : 1
(d) 3 : 1

A

Question. A particle of mass m is driven by a machine that delivers a constant power of k watts. If the particle starts from rest the force on the particle at time t is

D

Question. A block of mass 10 kg, moving in x direction with a constant speed of 10 ms–1, is subject to a retarding force F = 0.1 × J/m during its travel from x = 20 m to 30 m. Its final KE will be:
(a) 450 J
(b) 275 J
(c) 250 J
(d) 475 J

D

Question. A bomb of mass 1 kg is thrown vertically upwards with a speed of 100 m/s. After 5 seconds it explodes into two fragments. One fragment of mass 400 gm is found to go down with a speed of 25 m/s. What will happen to the second fragment just after the explosion? (g = 10 m/s2)
(a) It will go upward with speed 40 m/s
(b) It will go upward with speed 100 m/s
(c) It will go upward with speed 60 m/s
(d) It will also go downward with speed 40m/s

B

Question. The heart of man pumps 5 litres of blood through the arteries per minute at a pressure of 150 mm of mercury. If the density of mercury be 13.6 ×103 kg/m3 and g = 10m/s2 then the power of heart in watt is :
(a) 2.35
(b) 3.0
(c) 1.50
(d) 1.70

D

Question. Two particles A and B, move with constant velocities v1 and v2 . At the initial moment their position vectors are r1 and r2→ respectively. The condition for particles A and B for their collision is:

D

Question. A body projected vertically from the earth reaches a height equal to earth’s radius before returning to the earth. The power exerted by the gravitational force is greatest
(a) at the highest position of the body
(b) at the instant just before the body hits the earth
(c) it remains constant all through
(d) at the instant just after the body is projected

B

Question. A body of mass 1 kg begins to move under the action of a time dependent force F=(2tˆi+3tj) N, where ˆi and ˆj are unit vectors alogn x and y axis. What power will be developed by the force at the time t?
(a) (2t2 + 3t3)W
(b) (2t2 + 4t4)W
(c) (2t3 + 3t4) W
(d) (2t3 + 3t5)W

D

Question. A uniform force of (3iˆ+ ˆj) newton acts on a particle of mass 2 kg. The particle is displaced from position (2ˆi + kˆ) meter to position (4ˆi + 3ˆj – kˆ) meter. The work done by the force on the particle is
(a) 6 J
(b) 13 J
(c) 15 J
(d) 9 J

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 boy pushes a toy box 2.0 m along the floor by means of a force of 10 N directed downward at an angle of 60º to the horizontal. The work done by the boy is
(a) 6 J
(b) 8 J
(c) 10 J
(d) 12 J

C

Question. A particle moving in the xy plane undergoes a displacement of s 2iˆ+3 jˆ) while a constant force F = (5 iˆ + 2jˆ) N acts on the particle. The work done by the force F is
(a) 17 joule
(b) 18 joule
(c) 16 joule
(d) 15 joule

C

Question. A particle moves under the effect of a force F = cx from x = 0 to x = x1, the work done in the process is

B

Question. Two bodies A and B having masses in the ratio of 3 : 1 possess the same kinetic energy. The ratio of linear momentum of B to A is
(a) 1 : 3
(b) 3 : 1
(c) 1: 3
(d) 3 :1

C

Question. When a U238 nucleus, originally at rest, decays by emitting an a-particle, say with speed of v m/sec, the recoil speed of the residual nucleus is (in m/sec.)
(a) – 4 v/234
(b) – 4 v/238
(c) 4 v/238
(d) – v/4

A

Question. A motor of 100 H.P. moves a load with a uniform speed of 72 km/hr. The forward thrust applied by the engine on the car is
(a) 1111 N
(b) 3550 N
(c) 2222 N
(d) 3730 N

D

Question. A particle, initially at rest on a frictionless horizontal surface, is acted upon by a horizontal force which is constant in magnitude and direction. A graph is plotted of the work done on the particle W, against the speed of the particle v. If there are no other horizontal forces acting on the particle, the graph would look like

Question. A body moves a distance of 10 m along a straight line under the action of a force of 5 newtons. If the work done is 25 joules, the angle which the force makes with the direction of motion of body is
(a) 0º
(b) 30º
(c) 60º
(d) 90º

C

Question. Given that a force ˆF acts on a body for time t, and displaces the body by ˆd . In which of the following cases, the speed of the body must not increase?
(a) F > d
(b) F < d
(c) Fˆ = dˆ
(d) Fˆ ⊥ dˆ

D

Question. In figure, a carriage P is pulled up from A to B. The relevant coefficient of friction is 0.40. The work done will be
(a) 10 kJ
(b) 23 kJ
(c) 25 kJ
(d) 28 kJ

B

Question. A neutron with velocity v strikes a stationary deuterium atom, its K.E. changes by a factor of
(a) 15/16
(b) 1/2
(c ) 1/2
(d) None of these

D

Question. In the non-relativistic regime, if the momentum, is increase by 100% , the percentage increase in kinetic energy is
(a) 100
(b) 200
(c) 300
(d) 400

C

Question. A simple pendulum 1 metre long has a bob of 10 kg. If the pendulum swings from a horizontal position, the K.E. of the bob, at the instant it passes through the lowest position of its path is
(a) 89 joule
(b) 95 joule
(c) 98 joule
(d) 85 joule

C

Question. A ball is dropped from a height h. If the coefficient of restitution be e, then to what height will it rise after jumping twice from the ground?
(a) e h/2
(b) 2 e h
(c) e h
(d) e4 h

D

Question. A ball of mass m moving with a constant velocity strikes against a ball of same mass at rest. If e = coefficient of restitution, then what will be the ratio of velocity of two balls after collision?

A

Question. The potential energy of a conservative system is given by U = ay2 – by, where y represents the position of the particle and a as well as b are constants. What is the force acting on the system ?
(a) – ay
(b) – by
(c) 2ay – b
(d) b – 2ay

D

Question. A body is attached to the lower end of a vertical helical spring and it is gradually lowered to its equilibrium position. This stretches the spring by a length x. If the same body attached to the same spring is allowed to fall suddenly, what would be the maximum stretching in this case?
(a) x
(b) 2 x
(c) 3 x
(d) x/2

B

Question. A bag of mass M hangs by a long thread and a bullet (mass m) comes horizontally with velocity V and gets caught in the bag. Then for the combined (bag + bullet) system
(a) momentum = mvM/M+m
(b) kinetic energy = mV2/2
(c) kinetic energy = mV(M+m)/M
(d) kinetic energy = m2 v2/2(M+m)