9ii Work and Energy

When a body falls freely towards the earth, then its total energy

(a) increases

(b) decreases

(c) remains constant

(d) first increases and then decreases

A car is accelerated on a levelled road and attains a velocity 4 times of its initial velocity. In this process the potential energy of the car

(a) does not change

(b) becomes twice to that of initial

(c) becomes 4 times that of initial

(d) becomes 16 times that of initial

A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g = 10 ms²)

(a) 6 × 10³ J

(b) 6 J

(c) 0.6 J

(d) zero

Which one of the following is not the unit of energy?

(a) joule

(b) newton metre

(c) kilowatt

(d) kilowatt hour

Water stored in a dam possesses

(a) no energy

(b) electrical energy

(c) kinetic energy

(d) potential energy

If speed of a car becomes 2 times, its kinetic energy becomes

(a) 4 times

(b) 8 times

(c) 16 times

(d) 12 times

One joule work is said to be done when

(a) a force of 1 N displaces a body by 1 cm

(b) a force of 1 N displaces a body by 1 m

(c) a force of 1 dyne displaces a body by 1 m

(d) a force of 1 dyne displaces a body by 1 cm

SI unit of power is

(a) watt

(b) joule

(c) newton

(d) metre

Commercial unit of energy is

(a) joule

(b) kWh

(c) watt

(d) newton

 The spring will have maximum potential energy when

        (a) it is pulled out         (b) it is compressed

        (c) both (a) and (b)         (d) neither (a) nor (b)