(a) A ball of mass $0.5 \mathrm{kg}$slows down from a speed of $5 \mathrm{m}/\mathrm{s}$ to $3 \mathrm{m}/\mathrm{s}$, calculate the change in the kinetic energy of the ball.

(b) Which would have a greater effect on the kinetic energy of an object-doubling the mass or doubling the velocity.

Name the energy transformation taking place in the following devices:

(a)

(i) a motor

(ii) a car engine

(iii) a radio

(iv) a nuclear reactor

(b) How much work is done, when earth moves around the sun in its orbit.

A $5 \mathrm{kg}$ ball is thrown upwards with a speed of $10 \mathrm{m}/\mathrm{s}$.$\left(g\mathit{=}\mathit{10} \mathrm{m}/{\mathrm{s}}^2\right)$

(a) Calculate the maximum height attained by it

(b) Find the potential energy when it reaches the highest point.

Calculate the electricity bill amount for the month of April, if $4$ bulbs of $40 \mathrm{W}$ for$5$hrs, $4$ tube-lights of $60 \mathrm{W}$ for$5$ hrs a TV of $100 \mathrm{W}$ for $6$ hrs, a washing machine for $3$ hrs are used per day. The cost per unit is $₹ 1.80.$

An object is made to fall from different heights $20 \mathrm{cm}, 40 \mathrm{cm} \mathrm{and} 60 \mathrm{cm}$ on a wet sand.

(a) What do you observe on the sand?

(b) Explain the reason of your observation.

Define power. A boy of mass $45 \mathrm{kg}$ climbs up $20$steps in$20$ sec. It each step is $25 \mathrm{cm}$ high, calculate the power of the boy used in climbing. ($g\mathit{=}\mathit{10} \mathrm{m}/{\mathrm{s}}^2$)

(a) A truck and a car running with same velocity. Which of the two has less kinetic energy?

(b) Give an example of electrical energy converted into light energy.