A man stands on the roof of a 13.0 m -tall building and throws a rock with a vel

Question

A man stands on the roof of a 13.0 m -tall building and throws a rock with a velocity of magnitude 30.0 m/s at an angle of 42.0 above the horizontal. You can ignore air resistance.

A - Calculate the maximum height above the roof reached by the rock.

B - Calculate the magnitude of the velocity of the rock just before it strikes the ground.

C - Calculate the horizontal distance from the base of the building to the point where the rock strikes the ground.

Please explain how to do this with correct answers, thank you!

Explanation / Answer

Vx = 30*cos42° =22.29 m/s
t1 = 30 sin42/g = 1.05 sec
h1 = (30 sin42°)²/(2g) = 20.53 m (answer A)
H = 13 + h1 = 33.53 m
t2 = [2H/g] = 2.61sec
X = Vx*(t1 + t2) = 81.58 m (answer C)

Vf = [Vi² + 2*g*13] = 33.99 m/s (answer B)

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