Chapter 7, Problem 46A

A pair of 50-N weights are attached to a spring scale as shown. Does the spring scale read 0, 50, or 100 N? (Hint: Would it read any differently if one of the strings were held by your hand instead of being attached to the 50-N weight?)

To determine

Whether the spring scale read 0, 50, or 100 N.

Answer to Problem 46A

The spring scale reads $50\text{ N}$ .

Explanation of Solution

Introduction:

The expression for Newton’s third law of motion as follows:

  $F_{\text{x}}=-F_{\text{x1}}$

Here, $F_{\text{x1}}$ is the tension.

The spring scale produces the tension. Due to the 50 N weight, the tension on the spring scale is 50 N i.e. 50 N force is exerted on each end of the spring scale due to the 50 N weight.

Thus, the net force on the spring is zero due to the constant velocity. The spring scale produces only the tension force.

Conclusion:

Thus, the spring scale reads $50\text{ N}$ .