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A man named Harold is standing in a train car that has no windows. Since there aren't any windows, he doesn't know how fast or in what direction the train is moving or whether it is accelerating in the forward or backward direction. Harold decides that he might be able to figure something out by dropping a tennis ball and watching where it lands. He does know which way the front of the train is, so when he does his ball-drop experiment he is facing forward. To make his experiment easier, Harold draws a red X on the floor of the train car. He then holds the tennis ball directly over the X, and releases the ball from a height of about five feet.

The first time he drops the ball, it lands directly below his release point, right on the red X.
1)What can Harold conclude about the train's velocity?
a)The train is moving forward.
b)The train is moving backward.
c)The train isn't moving.
d)He hasn't learned anything about the train's velocity.

2)What can Harold conclude about the train's acceleration?
a) The train is undergoing forward acceleration.
b)The train is undergoing backward acceleration.
c)The acceleration is zero.
d)He hasn't learned anything about the train's acceleration.

A little while later, Harold tries his experiment again. This time, when he drops the ball, it lands behind the red X (in between his feet and the X).

3)What can Harold conclude about the train's velocity?
a)The train is moving forward.
b)The train is moving backward.
c)The train isn't moving.
d)He hasn't learned anything about the train's velocity.

4)What can Harold conclude about the train's acceleration?
a)The train is undergoing forward acceleration.
b)The train is undergoing backward acceleration.
c)The acceleration is zero.
d)He hasn't learned anything about the train's acceleration.

Harold is bored, because there really isn't anything to do when locked in a windowless train car. So he decides to entertain himself by doing the ball drop experiment one last time. This time, the ball lands in front of the red X (farther away from him than the red X).

5)What can Harold conclude about the train's velocity?
a)The train is moving forward.
b)The train is moving backward.
c)The train isn't moving.
d)He hasn't learned anything about the train's velocity.

6)What can Harold conclude about the train's acceleration?
a)The train is undergoing forward acceleration.
b)The train is undergoing backward acceleration.
c)The acceleration is zero.
d)He hasn't learned anything about the train's acceleration.

Explanation / Answer

(1)
d)He hasn't learned anything about the train's velocity.

(2)
c)The acceleration is zero.

(3)
d)He hasn't learned anything about the train's velocity.

(4)
a)The train is undergoing forward acceleration

(5)
d)He hasn't learned anything about the train's velocity.

(6)
b)The train is undergoing backward acceleration.

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