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

• b

• c

• d

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

• b

• c

• d

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

• a

• b

• c

• d

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

(a) joule

(b) newton metre

(c) kilowatt

(d) kilowatt hour

• a

• b

• c

• d

Water stored in a dam possesses

(a) no energy

(b) electrical energy

(c) kinetic energy

(d) potential energy

• a

• b

• c

• d

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

(a) 4 times

(b) 8 times

(c) 16 times

(d) 12 times

• a

• b

• c

• d

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

• a

• b

• c

• d

SI unit of power is

(a) watt

(b) joule

(c) newton

(d) metre

• a

• b

• c

• d

Commercial unit of energy is

(a) joule

(b) kWh

(c) watt

(d) newton

• a

• b

• c

• d

 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)

• a

• b

• c

• d