Question

A man of mass 80 kg sits on a platform suspended from a moveable pulley and raises himself at constant speed by a rope passing over a fixed pulley. Assuming No friction.

1-the force he must exerted

2-the increase in his energy when he rises himself 1 m

Answer 1

1)

$$F=W=mg\\F=(80)(9.8)=784\ N$$

2)

$$\Delta E=mgh\\\Delta E=(80)(9.8)(1)=784\ J$$