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


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




cool cool cool

CPhill  May 21, 2017

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