Posted by **Robert C** on Sunday, October 11, 2009 at 6:22pm.

A ball, dropped from rest, cover 2/7 of the distant to the ground in the last 2 seconds of its fall. From what height was the ball dropped? What was the total time of the fall?

- Physics -
**drwls**, Sunday, October 11, 2009 at 6:31pm
Let T be the total time to hit the ground.

Let H be the height it is dropped from.

H = (g/2) T^2

(5/7) H = (g/2)(T-2)^2

Two equations, two unknowns. H can be eliminated easily.

(5/7)H = (5/14) g T^2

(5/7)H = (g/2)(T-2)^2

Solve for T first, then solve for H

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