Calculate the amount of work needed to stop a car of 500 kg, moving at a speed of 36 km/h.

A man whose mass is 50 kg moves up 15 steps each of height 15 cm in 45 seconds of time. Calculate the power used in climbing those stairs. (g = 10 m/s²)

A battery lights a bulb. Describe the energy change involved in the process.

Rashmi was playing on a swing in a park. To increase her speed when her swing was at its lowest position during its oscillations she pushed the ground hard with her feet. She enjoyed it but could not understand the mechanism. Her elder brother Pankaj explained her the reason, when she asked him.

(i) What type of energy was possessed by Rashmi while swinging? On what factors does it depend?

(ii) Why did the swing’s speed increase on pushing the ground harder with feet?

(iii) Why and what did Rashmi ask Pankaj?

Roma enjoys to ride fastly on a swing. So Rano stands behind the swing every time Roma rides it and pushes her. However, Rano also gets scared of Roma riding too fast and keeps yelling out to her to be careful. However, Roma refrains from being slow.

(a) What energy conversion takes place on a swing?

(b) Muscular energy of Rano converts to which energy on pushing the swing?

(c) Compare the qualities of Roma and Rano.