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:
[tex]W=\Delta U=mg\Delta h[/tex]
where m=500 kg is the mass of the box, [tex]g=9.81 m/s^2[/tex] and [tex]\Delta h=4 m[/tex] is the variation of height of the box. Substituting these data into the equation, we find the work
[tex]W=mg\Delta h=(500 kg)(9.81 m/s^2)(4 m)=19620 J[/tex]
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:
[tex]P= \frac{W}{t}= \frac{19620 J}{100 s}=196.2 W [/tex]
