Consider the following three cases:.
Case 1: A person holds her arm at an angle of 30 degrees above the horizontal (hand is higher than the shoulder).
Case 2: A person holds her arm straight out parallel to the ground.
Case 3: A person holds her arm at an angle of 30 degrees below the horizontal (hand is lower than the shoulder).
(a) In which of the following cases is the torque about the shoulder due to the weight of the arm the greatest?
(b) Briefly explain your answer to the previous question.
(c) If the person lets her arm swing freely from an initial straight-out parallel-to-the-ground position, when is the angular acceleration of the arm about the shoulder the greatest?
(d) Briefly explain your answer to the previous question.