A rock is dropped off a cliff and strikes the ground with an impact velocity of 20m/s. How high was the cliff?(use a=-10m/s2)

20 m

Explanation:

by the formula,

                         2 x 10 x S = 20^2 - 0

                         20S = 400

                          S = 20 m  

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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2b2t

explanation:

2b2t