a 15kg rock falls from the top of a building 8.0m high. Find its PE and KE

a.when at rest at the top of the building
b. halfway down the ground
c. when it reaches the ground
d.speed when it reaches the ground

3 answers

make it clear for the answer

use 9.8 only

At time t seconds, the speed and height are given by

v = -9.8t
h = 8.0 - 4.9t^2

Then use the fact the the PE+KE must be constant

mgh + 1/2 mv^2 must stay the same.

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