Posted by **eric** on Thursday, February 24, 2011 at 9:42am.

One side of the roof of a building slopes up at 35.5°. A student throws a Frisbee onto the roof. It strikes with a speed of 15.0 m/s and does not bounce, but slides straight up the incline. The coefficient of kinetic friction between the plastic and the roof is 0.450. The Frisbee slides 10.0 m up the roof to its peak, where it goes into free-fall, following a parabolic trajectory with negligible air resistance. Determine the maximum height the Frisbee reaches above the point where it struck the roof.

- physics -
**Damon**, Thursday, February 24, 2011 at 9:53am
Well, I am not going to do it for you but will give some thoughts.

Approach it with energy reasoning.

The frisbee had kinetic energy when it hit the roof, (1/2) m v^2

It lost kinetic energy to potential climbing m g (10 sin 35.5)

It lost kinetic energy due to work done against friction

10 * .45 m g cos 35.5

subtract those two losses from initial Ke

That gives you the speed it departs the roof from Ke remaining =(1/2) m Vi^2

Now you have an ordinary projectile problem

departs the roof with vertical speed Vi sin 35.5

0 = Vi sin 35.5 - t 0

solve for t

H = 0 + Vi sin 35.5 t - 4.9 t^2

- physics -
**eric**, Thursday, February 24, 2011 at 9:54am
thanks for the help!

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