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Ball slided down incline and encounters rough surface

1.) A 1-kg ball starting at h = 7.2 meters slides down a smooth surface where it encounters a rough surface and is brought to rest at B, a distance 26.6 meters away. To the nearest joule what is the work done by friction?

2.) To two decimal places, what is the coefficient of friction?

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Solution Preview

By the law of conservation of energy, all the potential energy the ball had at the start is converted into kinetic energy at point A, and then, between the points A and B this kinetic energy is taken away from the ball by the friction.
Therefore the work done by friction is
W = - mgh

where m = 1 kg is the ...