A rock is suspended from a string and moves downward at constant speed. Which statement is true concerning the tension in the string if air resistance is ignored?
A)The tension is zero newtons.
B)The tension points downward.
C)The tension is equal to the weight of the rock.
D)The tension is less than the weight of the rock.
E)The tension is greater than the weight of the rock.

Question

Quizplus · Accepted Answer

If the rock is moving downward at a constant speed, the sum of the forces acting on the rock is zero. This means that the tension in the string, which is pulling the rock upward, must be equal in magnitude to the weight of the rock, which is pulling the rock downward. Therefore, the answer is C, the tension is equal to the weight of the rock.

A Rock Is Suspended from a String and Moves Downward