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True or false questions regarding the acceleration of an elevator.

An object of mass m is hanging by a string from the roof of an elevator. We want to compare the tension in the string to the weight of the object under various conditions. Which statements are true? (Give ALL correct answers)

A) If the elevator is moving upwards, but slowing down, the tension in the string is equal to the object's weight

B) If the elevator is moving downwards in free fall, the tension in the string is equal to the object's weight

C) If the elevator is moving downwards, and speeding up, the tension in the string is less than the object's weight

D) If the elevator is moving upwards, and speeding up, the tension in the string is less then the object's weight

E) If the elevator is moving up at constant speed, the tension in the string is equal to the object's weight

Solution Preview

A) If the elevator is moving upwards, but slowing down, the tension in the string is equal to the object's weight
<br>No. If the elevator, and hence the object, is going up but slowing down, this means the net force on the object is downwards, and the tension on the string is less than that needed to counter the gravitational force on the object.
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