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uic spig Conservative and Nonconservative Forces 7-5 38 A 1.00 kg block starts f

ID: 1779510 • Letter: U

Question

uic spig Conservative and Nonconservative Forces 7-5 38 A 1.00 kg block starts from rest at the top of a 20.0 m long 30.0 incline. Its kinetic energy at the bottom of the incline is 98.0 J. How much work is done by friction? 39 A 1.00 kg block slides down a 20.0 m long 30.0° in- cline at constant velocity. How much work is done by friction? 40 A ball of mass 0.300 kg is thrown upward, rising 10.0 m above the point at which it was released. Com- pute the average force exerted on the ball by the hand if the hand moves through a distance of 20.0 cm as the ball is accelerated. 41 A person jumps from a burning building onto a fire-

Explanation / Answer

initial energy of the block = potential energy

potential energy = mg * sin(theta) * d

potential energy = 1 * 9.8 * sin(30) * 20

potential energy = 98 J

final energy = kinetic enegy + work done by friction

by conservation of energy

initial energy = final energy

98 = 98 + work done by friction

work done by friction = 0 J