Perform the following paired movements, noting the difference in the effort needed. Diagram and explain the reasons for the difference.
A- A push-up from the toes and a push up from the knees.
B-A sit up with the hands on the thighs and a sit up with a 3 kg weight behind the head.
C-A 3 kg weight held in the hand with the arm outstretched horizontally sideward and a 3 kg weight suspended from the elbow crotch when the arm is outstretched sideward.