SOLUTION: A rock is thrown upward with a velocity of 21 meters per second from the top of a 48 meter high cliff, and it misses the cliff on the way back down. When will the rock be 7 meters

Question 1049275: A rock is thrown upward with a velocity of 21 meters per second from the top of a 48 meter high cliff, and it misses the cliff on the way back down. When will the rock be 7 meters from the water, below? Round your answer to two decimal places.

Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
A rock is thrown upward with a velocity of 21 meters per second from the top of a 48 meter high cliff, and it misses the cliff on the way back down. When will the rock be 7 meters from the water, below? Round your answer to two decimal places.
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You didn't supply the acceleration of Earth's gravity.
sometimes -10 m/sec/sec is used.
sometimes -9.8 m/sec/sec is used.
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Using 10 m/sec/sec:
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h(t) = -5t^2 + 21t + 48
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-5t^2 + 21t + 48 = 7
Solve for t.

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