Determining Speed given Horizontal and Vertical Distances

  • Thread starter Accolade
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  • #1
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Homework Statement


A girl throws a ball high into the air, and at its highest point it lands on a roof, where it gets stuck. You estimate the ball landed at a height of 21.0m from the ground and a horizontal distance of about 20.0m from where it was thrown. What is the speed that the girl threw the ball at?

Homework Equations


vfy = viy + ay(delta t)
vfy^2 = viy^2 + 2ay(delta y)
vfx = vix + ax(delta t)
x = vix (delta t) + 1/2(ax)(delta t)^2
y = viy (delta t) + 1/2 (ay) (delta t)^2
v = sqrt (vx^2) + (vy^2)

The Attempt at a Solution


It would take an enormous amount of space to replicate my work (and this would honestly be no better than spam), but the answer I found was 22.5 m/s. Please help me.
 

Answers and Replies

  • #2
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It wouldn’t help your understanding much for us to just tell you how to do it, so I’m afraid you will have to show us your attempts so we can subtly suggest and guide.

However, I can say it shouldn’t take an enormous amount of work. There is a straight forward approach with a couple of those equations that takes only a little work.
 

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