$A$ car and a truck are moving with the same velocity of $60\, km h^{-1}$. Which one has more kinetic energy? (Mass of truck $ > $ Mass of car).

$A$ light and a heavy object have the same momentum. Find out the ratio of their kinetic energies. Which one has a larger kinetic energy?

One joule of work is said to be done when:

$(i)$ $A$ light and a heavy object have the same momentum. What is the ratio of their kinetic energies? Which one has a larger kinetic energy?
$(ii)$ $A$ ball is dropped from a height of $10\, m$. If the energy of the ball reduces by $40\%$ after striking the ground,how high can the ball bounce back? $(g = 10\, m s^{-2})$

Justify,giving proper reasoning,whether the work done in the following case is positive or negative: Work done by friction on a body sliding down an inclined plane.

Define work. How is work measured? When is work done by a force negative?