An object of mass $40 \text{ kg}$ is pulled up to a height of $0.5 \text{ m}$. Calculate the work done. (Given $g = 9.8 \text{ m s}^{-2}$) (in $J$)

$A$ mass of $10 \, kg$ is dropped from a height of $50 \, cm$. Find its:
$(a)$ Potential energy just before dropping.
$(b)$ Kinetic energy just on touching the ground.
$(c)$ Velocity with which it hits the ground. (Given: $g = 10 \, m s^{-2}$)

State whether the following statement is true or false:
When an arrow is released from a bow,potential energy changes into kinetic energy.

State whether the following statement is true or false:
The rate of doing work is called power.

Give the formula for calculating work done. What is the $SI$ unit of work?

When is the work done by a force said to be negative? Give one situation in which one of the forces acting on the object is doing positive work and the other is doing negative work.