A man named Harold is standing in a train car that has no windows. Since there a
ID: 1586378 • Letter: A
Question
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 or decelerating. 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.
1. The first time he drops the ball, it lands directly below his release point, right on the red X.
I. 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.
II. 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.
2. 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).
I. 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.
II. 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.
3. 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).
I. 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.
II. 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)
(I) Object reaches at directly below its release point : From this we can conclude that either train is in rest or it is moving with constant velocity. As the train is moving the object is also moving with same speed .
ANS: D
(II) As mentioned above train is either in rest or in constant velocity so there is no acceleration .
ANS :C
(2)
(I) As the balls lands behind the spot so train is running either in forward direction with acceleration or backward direction with retardation .
ANS : D
(II) Here accelaration is in forward direction because retardation in backward direction is also taken as forward acceleration.
ANS: A
(3)
(I) Here train is moving either in forward direciton with retardation or backward direction with acceleration.
ANS: D
(II)Here accelaration is in backward direction because retardation in forward direction is also taken as backward acceleration.
ANS:B
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