A stone with a mass of 1.0 kg is tied to the end of a light string which keeps it moving in a circle with a constant speed of 4.0 m/s on a perfectly smooth horizontal tabletop.The radius of the path is 0.60 m.How much work does the tension in the string do on the stone as it makes one-half of a complete circle?
A)100 J
B)3.8 J
C)0 J
D)40 J
E)80 J

Question

Quizplus · Accepted Answer

The tension in the string is always perpendicular to the displacement of the stone, so the work done by tension is zero. The only force doing work is gravity, but it is also perpendicular to the displacement of the stone, so it does no work either. Therefore, the total work done on the stone is zero.

A Stone with a Mass of 1