A 0.875-kg ball is tied to the end of a string of length 1.70 m and swung in a v

ID: 585116 • Letter: A

Question

A 0.875-kg ball is tied to the end of a string of length 1.70 m and swung in a vertical circle.

a) During one complete circle, starting anywhere, calculate the total work done on the ball by the tension in the string.

b) During one complete circle, starting anywhere, calculate the total work done on the ball by gravity.

c) Repeat part (a) for motion along the semicircle from the lowest to the highest point on the path.

d) Repeat part (b) for motion along the semicircle from the lowest to the highest point on the path.

Work done by tension will be zero because at each point the tension force is perpendicular to the velocity or displacement hence F.dx = 0

b) Totol change in kinetic energy during one cycle is zero hence total work done is zero hence work done by gravity during one cycle will be zero.

c) The work done by tension force will always be zero.

d) The work done by force due to gravity will be -mgL as the direction of the force is opposite to the displacement.

W = F.dx = -mgh = -0.875*9.81*1.7 = -14.59 J

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