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April 21, 2014

April 21, 2014

Posted by **suzanne** on Thursday, February 28, 2013 at 1:45am.

- physics -
**drwls**, Thursday, February 28, 2013 at 2:32amNeglecting air friction, the time it will take the rock to hit the water is

sqrt(2H/g) = 2.857 seconds. That means the sound of the splash takes 3 - 2.857 = 0.143 seconds to be heard, after hitting water. Sound travelled 49.05 m in that time. Since the cliff is 40 m high, the horizontal distance travelled by the rock was (from the Pythagorean theorem)

sqrt[(49.05)^2 -(40)^2] = 28.4 m

The rock's initial speed (and constant horizontal speed) was 28.4 m/2.857 s = 9.84 m/s

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