1. What causes the boat in Fig. 4-41 to move forward?

(a) The force the man exerts on the paddle.
(b) The force the paddle exerts on the water.
(c) The force the water exerts on the paddle.
(d) The motion of the water itself.
2. A person stands on a scale in an elevator. His apparent weight will be the greatest when the elevator
(a) Is standing still.
(b) Is moving upward at constant velocity.
(c) Is accelerating upward.
(d) Is moving downward at constant velocity.
(e) Is accelerating downward.