Two objects,each of weight W,hang vertically by spring scales as shown in the figure.The pulleys and the strings attached to the objects have negligible weight,and there is no appreciable friction in the pulleys.The reading in each scale is
A) W.
B) more than W, but not quite twice as much.
C) less than W.
D) 2W.
E) more than 2W.

Question

Two objects,each of weight W,hang vertically by spring scales as shown in the figure.The pulleys and the strings attached to the objects have negligible weight,and there is no appreciable friction in the pulleys.The reading in each scale is 
A) W. 
B) more than W, but not quite twice as much. 
C) less than W. 
D) 2W. 
E) more than 2W.

Quizplus · Accepted Answer

Since the two objects are connected by a rope passing over a pulley, we know that they must be accelerating at the same rate. Therefore, the tension in the rope must be equal for both objects. Each scale is measuring the tension in the rope, which must be equal to the weight of one of the objects (since they have the same weight). Therefore, the reading in each scale is W.

Two Objects,each of Weight W,hang Vertically by Spring Scales as Shown