Finding maximum Height

  • #1

Homework Statement


A soccer ball is kicked at a 45° angle. If the ball is in the air for 3 s, what is the maximum height achieved

Homework Equations


y=viy + 0.5 x ay x t

The Attempt at a Solution


i used trig to get the vertical and horizontal components i got 2.2 for each side (as there the same with a 45 degree angle)

i used y=0 + 0.5 x (-9.81) x (3s)

is this right ^^
 

Answers and Replies

  • #2
176
19
your equation is not correct.
 
  • #3
i used y=0 + 0.5 x (-9.81) x (1.5s)Square root

is what i meant to put
 
  • #4
176
19
I think you mean squared, not square root.
 
  • #6
haruspex
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i got 2.2 for each side
You got 2.2 what? You don't know the velocity, so how can you get the velocity components?
What does your y0 represent?
 
  • #7
y=o represents initial velocity. but it is not known like you said, so that is how i was able to get 11.05 but setting initial to 0
 
  • #8
176
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The initial velocity cannot be 0. Otherwise, with gravity being the only accelerator the projectile would go down.
 
  • #9
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It's possible to calculate your initial velocity though, assuming the projectile lands on level ground. Can you modify your relationship above to help you find this?
 
  • #10
haruspex
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y=o represents initial velocity. but it is not known like you said, so that is how i was able to get 11.05 but setting initial to 0
Setting it zero will get you nowhere. Create an unknown for it, v.
Your equation for y is suitable for a vertical displacement, not a vertical velocity. In terms of v, what would the vertical displacement be at time t? What is the vertical displacement when it lands?
 
  • #11
I am trying to find displacement though
 
  • #12
haruspex
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I am trying to find displacement though
You are asked to find, eventually, the vertical displacement from launch to the highest point. I asked you what the vertical displacement is from launch to where it lands.
 

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