Problema Solution
a rock is thrown vertically downward from the building 40 m. high at an initial velocity of -15m/s. (a) what is the rocks velocity as its strikes the ground?(b)How long does it take for the rock to hit at the ground?
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Solution:
a.
vf2 = vi2 - 2gs
vf = -√((-15)2 - 2(-9.81)(40))
vf = -31.78 m/s
b.
t = (vf - vi)/g
t = (-31.78 + 15)/(-9.81)
t = 1.71 s