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

**2. Two bodies of masses m _{1} and m_{2} are moving with same kinetic energy. If P_{1} and P_{2} are their respective momentum, the ratio P_{1} P_{2} is equal to –**

- m
_{1}/m_{2} - sqrt(m
_{1}/m_{2}) - sqrt(m
_{2}/m_{1}) - m
_{2}/m_{1}

_{1}/m

_{2})

**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

**4. A simple pendulum with the bob of mass m and length x is held in position at an angle θ _{1} and then angle θ_{2} with the vertical. When released from these positions, speeds with which it passes the lowest positions are v_{1} & v_{2 }respectively. Then, v_{1}/v_{2} is**

- 1-cos θ
_{1}/1-cos θ_{2} - sqrt(1-cos θ
_{1}/1-cos θ_{2}) - sqrt(2gx(1-cos θ
_{1})/1-cos θ_{2}) - sqrt((1-cos θ1)/2gx(1-cos θ
_{2}))

_{1}/1-cos θ

_{2})

**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

**-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

**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

**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

**9. Two springs have force constant K _{1} and K_{2} (K_{1} > K_{2}). Each spring is extended by same force F. If their elastic potential energy are E_{1} and E_{2} then E_{1}/E_{2} is ?**

- K
_{1}/ K_{2} - K
_{2}/ K_{1} - √(K
_{2}/ K_{1}) - √(K
_{1}/ K_{2})

_{2}/ K

_{1}

**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

**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

**12. The power of water pump is 4 kW. If g = 10 m/s ^{2}, 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