Asked by Matt

looking over the edge of a cliff, you become curious as to how high up you are. you take a rock and drop it over the edge and count. The rock strikes the ground in between 3 and 4 of your count. so let's estimate that it took 3.5s for it to hit the ground. using the bottom of the cliff as y= 0m, estimate the height of the cliff assuming the rock was in freefall. start by identifying each known kinematic value from when the rock was falling:
a. is y0 known if so what is it?
b. is yf known if so what is it? 0m
c. is v0 known if so what is it?
d. is vf known if so what is it?
e is a known if so what is it? -9.8m/s
f. is t known if so what is it? 3.5s

This is as far as I got with my answers how can I figure the rest?
Answered by Damon
yf = yo + vo t + (1/2) a t^2

yf = 0
yo = unknown
vo = 0 (dropped not thrown)
vf irrelevant ( = a t)
a = -4.9 indeed
t = 3.5

so
0 = yo + 0 -4.9 (3.5)^2
or
yo = 4.9 (3.5)^2
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