What type of energy is stored in the spring of a watch?

Define work. Write an expression for work in terms of force and displacement. State the $SI$ unit of work done.

The potential energy of a person is minimum when:

$A$ boy is moving on a straight road against a frictional force of $5\, N$. After travelling a distance of $1.5\, km$ he reaches a roundabout (Fig.) of radius $100\, m$. He moves on the circular path for one and a half cycles and then moves forward up to $2.0\, km$. Calculate the total work done by him against the frictional force.

Does the work done in raising an object vertically depend upon how fast it is raised?

$A$ light and a heavy body have equal kinetic energy. Which one is moving fast?