Question

A rock is thrown horizontally off of a cliff. It starts with a velocity of 4.2 m/s and the cliff is
68.2 m high.

How long does the rock fall?
I got 3.7 seconds but I do not know if it is right.
(Help on these two)
How far out from the bottom of the cliff does the rock fall?
What is the rock’s velocity just before it hits the ground?

Answer 1

h = 0.5g*t^2 = 68.2 m.
4.9t^2 = 68.2
t^2 = 13.92.
t = 3.73 s.

Dx = Xo*t = 4.2m/s * 3.73s. = 15.7 m.

Yf^2 = Yo^2 + 2g*h.
Yf^2 = 0 + 19.6*68.2 = 1336.72.
Yf = 36.6 m.

Vf = sqrt(Xo^2 + Yf^2) = Final velocity.

Answer 2

Correction: Yf = 36.6 m/s.