Question

In the figure, the rock weighs 145 lb and is lifted 1 ft by the lever. (a) How much work is done (ft-lb)? (b) The other end of the lever is pushed down 3 ft while lifting the rock. What force had to act on that end (lbs)?

Answer 1

Given,

the weight of the stone is w = 145 lb

the height it raised is  d = 1 ft

we have work done is equal to the change in potential energy so

                        work done = wd = 145 ft-lb

b) here change in potential energies on both sides is same

so so let the force applied is F then we have

                  145 lb *1 ft = F * 3(d)

                                   F = 48.33 lb