# Physics

posted by Stark

A marble is thrown horizontally with a speed of 13.9 m/s from the top of a building. When it strikes the ground, the marble has a velocity that makes an angle of 40 ° with the horizontal. From what height above the ground was the marble thrown?

1. Damon

Vertical problem:
How fast does it fall?
(1/2) m v^2 = m g h
so
v = sqrt (2 g h)

Horizontal problem:
u = constant = 13.9

so

tan 40 = sqrt(2 g h) /13.9

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