A girl throws a rock horizontally, with a velocity of 10 m/ s, from a bridge. It falls 20 m to the water below. How far does the rock travel horizontally before striking the water?

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Answer 1 · 2015-11-07T23:21:22

$20.2"m"$

You use the vertical component of the motion to get the time of flight:

$s=1/2"g"t^2$

$:.t=sqrt((2s)/(g))$

$t=sqrt((2xx20)/(9.8))$

$t=2.02"s"$

Now we use the fact that the horizontal component of velocity is constant so:

$s=vxxt$

$:.s=10xx2.02=20.2"m"$