CBSE Class 11 Physics Work Energy and Power Worksheet Set A

Question. Which of the following force(s) is/are non-conservative?
(a) Frictional force
(b) Spring force
(c) Elastic force
(d) All of these

Answer: A

Question. The work done in stretching a spring of force constant k from length l₁ and l₂ is 

Answer: B

Question. If the force acting on a body is inversely proportional to its velocity, then the kinetic energy acquired by the body in time t is proportional to
(a) t⁰
(b) t¹
(c) t²
(d) t⁴

Answer: B

Question. The vessels A and B of equal volume and weight are immersed in water to depth h. The vessel A has an opening at the bottom through which water can enter. If the work done in immersing A and B are WA and WB respectively, then
(a) W_A = W_B
(b) W_A < W_B
(c) W_A > W_B
(d) WA > < WB

Answer: B

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
(a) 2 Mg l
(b) Mg l
(c) Mgl/2
(b) Mgl/4

Answer: 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
(a) mv₁ t/t₂
(b) mv₁² t/t₁
(c) mv₁ t²/t₁
(d) mv₁² t/t₁²

Answer: D

Question. A block is acted upon by a force, which is inversely proportional to the distance covered (x). The work done will be proportional to
(a) x
(b) x^1/2
(c) x²
(d) None of these

Answer: D

Question. A small body is projected in a direction inclined at 45º to the horizontal with kinetic energy K. At the top of its flight, its kinetic energy will be
(a) Zero
(b) K/2
(c) K/4
(d) K/√2

Answer: B

Question. A motor cycle is moving along a straight horizontal road with a speed v₀. If the coefficient of friction between the tyres and the road is m, the shortest distance in which the car can be stopped is
(a) v₀²/2μg
(b) v²/μ
(c) (v₀/μg)²
(d) v_0/μg

Answer: A

Question. Consider the following two statement:
I. Linear momentum of a system of particles is zero.
II. Kinetic energy of a system of particles is zero.
Then
(a) I implies II but II does not imply I.
(b) I does not imply II but II implies I.
(c) I implies II and II implies I.
(d) I does not imply II and II does not imply I.

Answer: B

Question. Which of the following must be known in order to determine the power output of an automobile?
(a) Final velocity and height
(b) Mass and amount of work performed
(c) Force exerted and distance of motion
(d) Work performed and elapsed time of work

Answer: D

Question. A body is dropped from a height of 20m and rebounds to a height 10m. The loss of energy is
(a) 10%
(b) 45%
(c) 50%
(d) 75%

Answer: C

Question. A cord is used to lower vertically a block of mass M, a distance d at a constant downward acceleration of g/4. The work done by the cord on the block is
(a) Mg d/4
(b) 3Mg d/4
(c) -3Mg d/4
(d) Mg d

Answer: C

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

Answer: C

Question. The engine of a truck moving along a straight road delivers constant power. The distance travelled by the truck in time t is proportional to
(a) t
(b) t²
(c) √t
(d) t³/2

Answer: D

Question. A bullet of mass ‘a’ and velocity ‘b’ is fired into a large block of wood of mass ‘c’. The bullet gets embedded into the block of wood. The final velocity of the system is 
(a) b/a+b x c 
(b) a+b/c x a
(c) a/a+c x b
(d) a+c/a x b

Answer: 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

Answer: D

Question. The magnitude of work done by a force :
(a) depends on frame of reference
(b) does not depend on frame of reference
(c) cannot be calculated in non-inertial frames.
(d) both (a) and (b)

Answer: A

Question. Figure here shows the frictional force versus displacement for a particle in motion. The loss of kinetic energy in travelling over s = 0 to 20 m will be
(a) 250 J
(b) 200 J
(c) 150 J
(d) 10 J

Answer: A

Question. Two solid rubber balls A and B having masses 200 & 400 gm respectively are moving in opposite direction with velocity of A equal to 0.3 m/sec. After collision the two balls come to rest when the velocity of B is
(a) 0.15 m/sec
(b) 1.5 m/sec
(c) –0.15 m/sec
(d) None of these

Answer: A

Question. A bomb of mass 9 kg explodes into the pieces of masses 3 kg and 6 kg. The velocity of mass 3 kg is 16 m/s. The kinetic energy of mass 6 kg in joule is
(a) 96
(b) 384
(c) 192
(d) 768

Answer: C

Question. Work done by a conservative force is positive if
(a) P.E. of the body increases
(b) P.E. of the body decreases
(c) K.E. of the body increases
(d) K.E. of the body decreases

Answer: B

Question. Which one of the following physical quantities is represented by the shaded area in the given graph? 
(a) Torque
(b) Impulse
(c) Power
(d) Work done

Answer: D

Question. A particle of mass m1 moving with velocity v collides with a mass m2 at rest, then they get embedded. Just after collision, velocity of the system
(a) increases
(b) decreases
(c) remains constant
(d) becomes zero

Answer: B

Question. The engine of a vehicle delivers constant power. If the vehicle is moving up the inclined plane then, its velocity,
(a) must remain constant
(b) must increase
(c) must decrease
(d) may increase, decrease or remain same.

Answer: A