The work done is equal to the change in potential energy which is the

mass times the chage in height times the acceleration due to gravity.

This comes to the same thing as the force times the distance it moves

through as the force is the mass times the acceleration due to gravity

and the distance moved through is the change in height.

The time here is a noise parameter it has nothing to do with the work done2. Y lifts a 1 kg mug to a height of 2.5m in 5 seconds. How much work does Y do?

which is calculated in exactly the same way as in part (1).

To do this we ignore drag terms and so:3. Ship = 4 500 tonnes, engine provides thrust force of 90 000N. What is teh shortest time in which teh ship can accelerate from 10-28 kms/hr?

force=mass x acceleration.

Here we have a constant mass 4500 tonnes=4500000 kg, the acceleration

will also be constant, and so acceleration = change in velocity/time

(you will have to convert the velocities into m/s).

The force is the thrust 90000N.

Plug these into the first equation and solve for time.

RonL