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August 28, 2014

August 28, 2014

Posted by **brittany** on Sunday, January 31, 2010 at 7:36pm.

- physics -
**Damon**, Sunday, January 31, 2010 at 7:47pmfirst get time to fall to ground

a = -9.8

v = -9.8 t

-15 = -4.9 t^2

t = sqrt (15/4.9) = 1.75 seconds

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Now how long did it take to reach 3.1 m down

3.1 = -4.9t^2

t = .795 seconds

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so the second rock spends 1.75 -.795 or .955 seconds in the air

-15 = Vo (.955) -4.9 (.955)^2

.955 Vo = 3.64-15

Vo = - 11.9

so 11.9 m/s downward (negative)

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