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PLEASE HELP... 100 POINTS....

question) A 100 kg rock sits on top of a 80-meter cliff. If the rock falls, how fast is it going at 20 m? Ignore air resistance.

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HamK

Answer: 20 m/s in 2 significant figures.

Explanation:

Initial velocity (u) = 0 m/s

Acceleration by gravity (a) = 9.81 m/s^2

Displacement (s) = 20m

Final velocity (v) = ?

Now, use formula

v^2 = u^2 + 2 * a * s

or, v^2 = 0^2 + 2 * 9.81 * 20

or, v = square root of( 2 * 9.81 * 20 )

So, v = 20 m/s in 2 significant figures.

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