One side of the roof of a building slopes up at 38.0°. A roofer kicks a round, f
ID: 1591676 • Letter: O
Question
One side of the roof of a building slopes up at 38.0°. A roofer kicks a round, flat rock that has been thrown onto the roof by a neighborhood child. The rock slides straight up the incline with an initial speed of 15.0 m/s. The coefficient of kinetic friction between the rock and the roof is 0.390. The rock slides 10.0 m up the roof to its peak. It crosses the ridge and goes into free fall, following a parabolic trajectory above the far side of the roof, with negligible air resistance. Determine the maximum height the rock reaches above the point where it was kicked.
Explanation / Answer
On the roof,
a = g(-sin - µcos) = -9.0452 m/s²
At the ridge,
V1 = [Vo² + 2as] = [15² - 2*9.0452*10] = 6.640 m/s @ 38°
Hmax = 10*sin38 + V1²*sin²/2g = 10.50 m
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