Lakhmir Singh and Manjit Kaur Solutions for Chapter: Work and Energy, Exercise 13: Long Answer Type Questions

What do you understand by the kinetic energy of a body?

A body is thrown vertically upwards. Its velocity goes on decreasing. What happens to its kinetic energy as its velocity becomes zero?

A horse and a dog are running with the same speed. If the weight of the horse is ten times that of the dog, what is the ratio of their kinetic energies?

Explain by an example what is meant by potential energy. Write down the expression for gravitational potential energy of a body of mass $m$ placed at a height $h$ above the surface of the earth.

What is the difference between potential energy and kinetic energy?

A ball of mass $0.5 \text{kg}$ slows down from a speed of $5 \raisebox{1ex}{$\text{m}$}\!\left/ \!\raisebox{-1ex}{$\text{s}$}\right.$ to that of $3\raisebox{1ex}{$\text{ m}$}\!\left/ \!\raisebox{-1ex}{$\text{s}$}\right.$. Calculate the change in kinetic energy of the ball. State your answer giving proper units. 

What is the difference between gravitational potential energy and elastic potential energy? Give one example of a body having gravitational potential energy and another having elastic potential energy.

If $784 \mathrm{J}$ of work was done in lifting a $20 \mathrm{k}\mathrm{g}$ mass, calculate the height through which it was lifted. $\left(\mathrm{g}=9.8 \raisebox{1ex}{$\text{m}$}\!\left/ \!\raisebox{-1ex}{${\text{s}}^2$}\right.\right)$