SOLUTION: On the moon, the acceleration due to gravity is -1.6 meters per second per second. A stone is dropped from a cliff on the moon and hits the surface of the moon 20 seconds later.

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Question 287520: On the moon, the acceleration due to gravity is -1.6 meters per second per second. A stone is dropped from a cliff on the moon and hits the surface of the moon 20 seconds later.
a)How far did it fall?
b)What was its velocity at impact?

Answer by Edwin McCravy(20062) About Me  (Show Source):
You can put this solution on YOUR website!
On the moon, the acceleration due to gravity is -1.6 meters per second per second. A stone is dropped from a cliff on the moon and hits the surface of the moon 20 seconds later.
a)How far did it fall? 

h = h0 + v0t + 1%2F2at2

When the stone is dropped, the height above the moon's surface is
h0.  That is the unknown we want to find.

Since the stone is merely dropped, not thrown down, v0 = 0.

After t = 20 seconds, the height above the moon's surface is h = 0.

Substituting these, along with a = -1.6m%2Fs%5E2 

0 = h0 + (0)t + 1%2F2(-1.6)(20)2

Simplifying:

0 = h0 - 320

Solving that gives:

h0 = 320 meters.

b)What was its velocity at impact?

We use the formula which is the derivative of
 the formula used in part (a), namely

v = v0 + at

v = 0 + (-1.6)(20)

v = -32m%2Fs

The reason the velocity is negative is because the stone 
is going downward.

Edwin