Two 100-N weights are attached to a spring scale as shown. Does the scale read 0, 100, or 200 N, or does it give some other reading? (?Hint: Would it read any differently if one of the ropes were tied to the wall instead of to the hanging 100-N weight?)
100 N, the same reading it would have if one of the ends were tied to the 100 N hanging weight. Although the net force on the system is zero, the tension in the rope within the system is 100 N, as shown on the above figure on the scale reading. This means the tension in the string is 100 N. So the scale will read 100 N.