These Objective Questions on Work, Energy and Power (Class XI, Physics) will help you in preparing for different examinations like AIEEE, AIPMT, IIT, and other +2 level competitive exams, and will also help in many government exams that ask the basics of physics.

1. When the momentum of a body increases by 200%, its KE increases by how much percent ?

  • 100
  • 200
  • 400
  • 800
Answer
800

2. Two bodies of masses m1 and m2 are moving with same kinetic energy. If P1 and P2 are their respective momentum, the ratio P1 P2 is equal to –

  • m1/m2
  • sqrt(m1/m2)
  • sqrt(m2/m1)
  • m2/m1
Answer
sqrt(m1/m2)

3. KE acquired by a mass m in travelling a certain distance d, starting from rest, under the action of a constant force F is ?

  • Directly proportional to m
  • Directly proportional to √m
  • Directly proportional to 1/m
  • None of these
Answer
None of these

4. A simple pendulum with the bob of mass m and length x is held in position at an angle θ1 and then angle θ2 with the vertical. When released from these positions, speeds with which it passes the lowest positions are v1 & v2 respectively. Then, v1/v2 is

  • 1-cos θ1/1-cos θ2
  • sqrt(1-cos θ1/1-cos θ2)
  • sqrt(2gx(1-cos θ1)/1-cos θ2)
  • sqrt((1-cos θ1)/2gx(1-cos θ2))
Answer
sqrt(1-cos θ1/1-cos θ2)

5. A U–238 nucleus originally at rest, decays by emitting a α-particle, say with a velocity of v m/s. The recoil velocity (in m/s) of the residual nucleus is ?

  • -4v/234
  • v/234
  • v/4
  • 4v/238
Answer
-4v/234

6. The total work done on a particle is equal to the change in its kinetic energy. This is applicable –

  • Always
  • Only if the conservative forces are acting on it
  • Only in inertial frames
  • Only when pseudo forces are absent
Answer
Always

7. Potential energy is defined – 

  • Only in conservative fields
  • As the negative of work done by conservative forces
  • As the negative of work done by external forces when ΔK = 0
  • All of these
Answer
Only in conservative fields

8. A spring with spring constants ‘k’ when compressed by 1 cm, the potential energy stored is U. If it is further compressed by 3 cm, then the change in its potential energy is ?

  • 3U
  • 9U
  • 8U
  • 15U
Answer
15U

9. Two springs have force constant K1 and K2 (K1 > K2). Each spring is extended by same force F. If their elastic potential energy are E1 and E2 then E1/E2 is ?

  • K1 / K2
  • K2 / K1
  • √(K2 / K1)
  • √(K1 / K2)
Answer
K2 / K1

10. An unloaded bus can be stopped by applying brakes on a straight road after covering a distance x. Suppose, the passenger add 50% of its weight as the load and the braking force remains unchanged, how far will the bus go after the application of the brakes ? (Velocity of bus in both cases is same)

  • Zero
  • 1.5x
  • 2x
  • 2.5x
Answer
1.5x

11. Initially, mass m is held such that spring is in a relaxed condition. If mass m is suddenly released, maximum elongation in the spring will be ?

  • mg / k
  • 2mg/k
  • mg/2k
  • mg/4k
Answer
2mg/k

12. The power of water pump is 4 kW. If g = 10 m/s2, the amount of water it can raise in 1 minute to a height of 20 m is (1 litre = 1Kg)

  • 100 litre
  • 1000 litre
  • 1200 litre
  • 2000 litre
Answer
1200 litre

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