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)