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A boy is standing on a 19.6 m high bridge sees a motorboat approaching the bridge at a constant speed. When the boat is 27 m from the bridge, the boy drops a stone to the water below. If the stone strikes the water 3.0 m in front of the boat, at what speed is the boat traveling?

 

I got V = 12 m/s but I would like to know if it is correct so I know I'm on the right track for the rest of the problems.

Guest Oct 15, 2018
 #1
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The time for the  stone to fall can be calculated by

 

0  = -4.9t^2  + 19.6

 

-19.6  = -4.9t^2

 

t^2 =  19.6 / 4.9  

 

t  =sqrt (19.6 / 4.9)  = 2 seconds

 

The boat must travel  27 - 3  =  24 m  in this time

 

So

 

D / T  = R

 

24 /2   = 12m/s        you are correct!!!!

 

 

 

cool cool cool

CPhill  Oct 15, 2018

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