A 0.840-kg ball is tied to the end of a string of length 1.57 m and swung in a v

ID: 1583000 • Letter: A

Question

A 0.840-kg ball is tied to the end of a string of length 1.57 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.

a. for complete circle the ball reaches the same position where it starts....hence displacement is zero ..then workdone is zero

b. here also complete circle ..w = 0

c, for semicircular path displacement is s = 2r = 2 (1,57) = 3.14m

during this path the tentional force always perpendicular to the displacement ...so angle is 90

w = F s cos(90) =0J

d. workdone by gravity w = F s cos(180) = - mg (2r) = 0.84*9.8*3.14 = -25.85J

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