Question

3. With the help of a movable roller the load is lifted, weighing 240 kg, at a height of 1.5 m, exerting the force 1434 N. Find the useful work and the efficiency of the roller.

Answer 1

Find the change in potential energy (work done against gravity):

$$W=mgh.$$

Efficiency:

$$\eta=\frac{Fh}{mgh}100\%=\frac{F}{mg}100\%=61\%.$$