In each of the situations below calculate the change in potential energy. In each case the box has a mass of 2.1kg.

a) A box starts on a floor is raised up 2.3m, and then lowered to the top of a table which is 1.1m tall.

b) A box starts on top of a 1.1m tall table and then is moved 1.2m across the table to the other side.

c) A box initially compresses a spring with spring constant of 3.4N/m 4.5cm from equilibrium. It ends with the spring extended 1.3cm from equilibrium.