Question

Jill pulls on a rope to lift a 12 kg pail out of a well, while the clumsy Jack watches. For a 10.0 meter segment of the lift, she lifts the bucket straight up at constant speed. How much power is required to complete this task in 5.0 seconds?

Answer 1

Definition of power is the amount of work done per unit of time:
$P=\frac{W}{t}$
We need to calculate the work done by Jill. 
Work is defined as the force acting along the path: 
$W=F\cdot h$
In this case, Jill is working against the force of gravity along the path of 10 meters:
$W=mgh=12\cdot9.81\cdot 10=1177.2 J$
Now we can calculate the power:
$P=\frac{1177.2}{5}= 235.44 W$