When designing elevators, it is important to consider the maximum tension a cabl

Question

When designing elevators, it is important to consider the maximum tension a cable will support. Which of the following causes a maximum tension? Select one: a. moving at a constant velocity b. accelerating upward c. accelerating downward d. Tension does not depend on the motion of the elevator.

When designing elevators, it is important to consider the maximum tension a cable will support. Which of the following causes a maximum tension?

Select one:

a. moving at a constant velocity

b. accelerating upward

c. accelerating downward

d. Tension does not depend on the motion of the elevator.

Explanation / Answer

b. accelerating upward

For constant velocity, the tension is only equal to the weight of the cab plus its occupants, exactly as it would, when the elevator cab is stationary.

For accelerating downward, the tension is "relieved" slightly of its duty to hold the cab's weight. Some of the cab's weight contributes to the downward acceleration, and thus must exceed the tension. The tension is therefore less than the weight of the cab plus its occupants.

For accelerating upward, not only must the tension fully support the cab + occupants weight, it must also provide the net force needed to accelerate the cab upward. Thus, the tension exceeds weight in this case.

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