Heat and work are equivalent. This means,
A. when we supply heat to a body we do work on it

B. when we do work on a body we supply heat to it

C. the temperature of a body can be increased by doing work in it.

D. a body kept at rest may be set into motion along a line supplying heat to it.

A ball is dropped on a floor from a height of 2.0 m. After the collision it rises up to a height of 1.5 m. Assume that 40% of the mechanical energy lost goes as thermal energy into the ball. Calculate the rise in the temperature of the ball in the collision. Heat capacity of the ball is 800 J K^–1.

A van of mass 1500 kg travelling at a speed of 54 km h^–1 is stopped in 10 s. Assuming that all the mechanical energy lost appears as thermal energy in the brake mechanism, find the average rate of production of thermal energy in cal s^–1.

Heat and work are equivalent. This means,

The temperature of a solid object is observed to be constant during a period. In this period.

A 50 kg man is running at a speed of 18 km h^–1. If all the kinetic energy of the man can be 9used to increase the temperature of water from 20°C to 30°C, how much water can be heated with this energy?

A copper cube of mass 200 g slides down on a rough inclined plane of inclination 37° at a constant speed. Assume that any loss in mechanical energy goes into the copper block as thermal energy. Find the increase in the temperature of the block as it slides down through 60 cm. Specific heat capacity of copper = 420 J kg^–1 K^–1.

Two blocks of masses 10 kg and 20 kg moving at speeds of 10 m s^–1 and 20 m s^–1 respectively in opposite directions, approach each other and collide. If the collision is completely inelastic, find the thermal energy developed in the process.

Calculate the time required to heat 20 kg of water from 10°C to 35°C using an immersion heater rated 1000 W. Assume that 80% of the power input is used to heat the water. Specific heat capacity of water = 4200 J kg^–1 K^–1.

Indian style of cooling drinking water is to keep it in a pitcher having porous walls. Water comes to the outer surface very slowly and evaporates. Most of the energy needed for evaporation is taken from the water itself and the water is cooled down. Assume that a pitcher contains 10 kg of water and 0.2 g of water comes out per second. Assuming no backward heat transfer from the atmosphere to the water, calculate the time in which the temperature decreases by 5°C. Specific heat capacity of water = 4200 J kg^–1 °C^–1 and latent heat of vaporization of water = 2.27 × 10⁶ J kg^–1.

On a winter day the temperature of the tap water is 20°C whereas the room temperature is 5°C. Water is stored in a tank of capacity 0.5 m³ for household use. If it were possible to use the heat liberated by the water to lift a 10 kg mass vertically, how high can it be lifted as the water comes to the room temperature? Take g = 10 m s^–2.