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A rock is dropped off a cliff and strike...

A rock is dropped off a cliff and strikes the ground with an impact velocity of `30 m//s`. How high was the cliff ?

A

15m

B

20m

C

30m

D

45 m

Text Solution

Verified by Experts

The correct Answer is:
D
Use Big Five #5 with `v_(0)=0` (calling down the positive direction).
`v^(2)= v_(0)^(2)+2aDelta s = 2a Delta s implies Delta s = (v^(2))/(2 a)=(v^(2))/(2g)=((30 m//s)^(2))/(2(10 m//s^(2)))=45 m`
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