A soccer ball leaves a cliff 20.2 m above the valley ﬂoor, at an angle of 10 degrees above the horizontal. The ball hits the valley floor 3.0 seconds later. What is the initial velocity of the ball?

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Answer 1 · 2015-12-02T15:56:32

#46.05"m/s"#

The situation looks like this:

hyperphysics.phy-astr.gsu.edu

I will adopt a convention that "up is positive". This means that #y# will be -ve in this scenario.

We can use:

#s=ut+1/2at^2#

This becomes:

#y=v(sintheta)t-1/2"g"t^2#

#:.-20.2=3vsintheta-1/2xx9.8xx3^2#

#:.3vsintheta=44.1-20.2=23.9#

#:.v=(23.9)/(3sin10)#

#v=(23.9)/(3xx0.173)=46.05"m/s"#