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# If an object falls from a height of h mts, t seconds after starting the fall has traveled a distance of

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If an object falls from a height of h mts, t seconds after starting the fall has traveled a distance of

s(t)=-4.9t^2 + h

A workman drops a wrench from a height of 50 meters and shouts: be careful down there!

How long should a person stay away from the path of the key?  At what speed does the key touch the ground?

Guest May 21, 2017
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As an answer to the first part we have

0  = -4.9t^2 + 50       subtract 50 from both sides

-50  =  -4.9 t^2         divide both sides by -4.9

50 / 4.9  =  t^2         take the positive root of both sides

√(50/4.9)  =  t  ≈  3.2 seconds

As an answer to the second part we have

-9.8 (3.2)   ≈  31.36 m / s

CPhill  May 21, 2017

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