Answer
(a) Two. (b) Weight and the applied force by the hand. (c) They are unequal in magnitude but in opposite directions. (d) No.
Work Step by Step
(a & b) There are two forces present, the weight of the brick $W$ and the applied force $F$ from the hand upward. (c) If the brick is accelerating upward, there must be a net force. This means that the forces cannot be equal in magnitude. However, the forces are opposite in direction, with weight acting downward and the applied force moving upward. (d) One of the forces is not caused by the other. Therefore, the forces are not an action-reaction pair.
