10 QA on work power energy | Learn Physics

10 Question-Answer on work power energy

1.       If two protons are brought near one another, the potential energy of the system will:

(a)    Increase

(b)   Decrease

(c)    Remain the same

(d)   Equal to the kinetic energy

Ans:  (a)

2.       A water pump driven by petrol raises water at a rate of 0.5 m³/min. from a depth of 30 m. If the pump is 70% efficient the power developed by the engine is:

(a)    1750 W

(b)   2450 W

(c)    3500 W

(d)   7000 W

Ans: ( c)

 

3.       The energy required to accelerate a car from 10 m/s to 20 m/s is n times the energy required to accelerate the same from rest to 10 m/s, where n is :

(a)    1

(b)   4

(c)    2

(d)   3

Ans: ( d)

 

4.       A man is riding on a cycle with velocity 7.2 km/h up a hill having a slope 1 in 20. Total mass of the man and cycle is 100 kg. The power of a man is:

 

(a)    98 W

(b)   49 W

(c)    196 W

(d)   147 W

Ans : (a)

5.       A body is moving under the action of a force. Suddenly, force is increased to such an extent that its kinetic energy is increased by 100%. The momentum increases by:

(a)    100%

(b)   60%

(c)    40%

(d)   20%

Ans: (c )

6.       The slope of potential energy versus position graph represents

(a)    Force

(b)   Work

(c)    Power

(d)   Momentum

Ans: ( a)

7.       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 60˚ to the horizontal The work done by the boy is:

(a)    6 J

(b)   8 J

(c)    10 J

(d)   12 J.

Ans: (c)

8.       Tape recorder records the sound in the form of :

(a)    Electrical energy

(b)   Magnetic field on the tape

(c)    Variable resistance on the tape

(d)   Sound wave held on the tape

Ans: (b)

9.       What is the shape of the graph between the speed and kinetic energy of a body?

(a)    Straight line

(b)   Hyperbola

(c)    Parabola

(d)   Exponential

Ans: (c )

10.   The negative of the work done by the conservative internal force on a system equals the change in:

(a)    Potential energy

(b)   Kinetic energy

(c)    Total energy

(d)   None of these

Ans: (a)