posted by eric on .
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.
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
thanks for the help!