A fitness enthusiast is trying to strengthen his calf muscles. 

He uses the exercise machine below. His heels apply a force to the padded bar. This lifts the heavy weights.

a. The centre of mass of the weights is at C. Draw a diagram to show where and in which direction the force of gravity acts on the weights. Label this force W. 

b. The narrow steel bar is padded. Why does this feel more comfortable when lifting the weights? 

c. The heels press against the pad with a force F and cause a turning effect about the pivot. Calculate the value of F when the weights are in the position shown in the diagram. Show your working. 

d. Why does it become harder to lift the weights when they move to the right?

end of horizontal steel bar 0.25 m - padding for bar pivot metal frame 250 N weights -- *** 40.2 m