Question

A forklift holds a 500 kg box 4 m in the air for 100 s. what is the minimum power required by the forklift

Answer 1

First of all, we need to calculate the work done by the forklift to lift the box of 500 kg by 4 meters. The work done is equal to the variation of gravitational potential energy of the box, given by:
$W=\Delta U=mg\Delta h$
where m=500 kg is the mass of the box, $g=9.81 m/s^2$ and $\Delta h=4 m$ is the variation of height of the box. Substituting these data into the equation, we find the work
$W=mg\Delta h=(500 kg)(9.81 m/s^2)(4 m)=19620 J$

And now we can calculate the minimum power required by the forklift, which is equal to the ratio between the work done and the time taken:
$P= \frac{W}{t}= \frac{19620 J}{100 s}=196.2 W$