Question

A woman uses a pulley and a rope to raise a 12 kg weight to a height of 2 m . Part A If it takes 4 s to do this, about how much power is she supplying?

Answer 1

To solve this problem it is necessary to apply the concepts related to work and power.

Remember that work is defined as the force applied on a body - or exerted by it - to travel a certain distance, and that the power is that energy mentioned to perform that activity in a given instance of time.

Mathematically work is defined as

$W = Fd$

Where

$F = Force \rightarrow mass*acceleration$

d = Distance

At this case the acceleration is the same that gravitational acceleration

At the same time we have that power is defined as

$P = \frac{W}{\Delta t}$

Replacing our values we have that the Work done was

$W = mg*d$

$W = (20)(9.81)(2)$

$W = 392.4J$

Now substituting this value at the Power equation we have

$P = \frac{392.4J}{4s}$

$P = 100W$

Therefore the power that she is supplying is 100W.