Question

A 8.00 kg box is pulled by a horizontal wire in a circle on a rough horizontal surface for which the coefficient of kinetic friction is 0.300.

A. Calculate the work done by friction during one complete circular trip if the radius is 2.00 m .

B. Calculate the work done by friction during one complete circular trip if the radius is 4.00 m .

Answer 1

M = 8.00 kg m k = 0.300 (a) calculate work done (w) radius is 2.00 m w = > m gamma g = > 8.00 gamma 9.8 = > 78.4 N (downward) normal reaction of the ground (f_ n) = -w = > -78.4 n(upward) therefore tangential components friction force (f_ f) mu k gamma N = > 0.300 gamma 78.4 = > 23.52 N Distance (b) = > 2 pi r = > 2 pi (2.00 m) = > 12.56 m therefore work done by friction f gamma 2 pi r = > -23.52 gamma 12.56 = > -295.415 (b)r = > 23.52 N distance (D) = 2 pi r = > s pi (4.00) = > 25.13 m work done by friction = > -8 gamma 2 pi r = > -23.52 gamma 25.13 = > -591.055