# Finding maximum Height

1. May 25, 2016

### pennywise1234

1. The problem statement, all variables and given/known data
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

2. Relevant equations
y=viy + 0.5 x ay x t

3. 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 ^^

2. May 25, 2016

### rpthomps

3. May 25, 2016

### pennywise1234

i used y=0 + 0.5 x (-9.81) x (1.5s)Square root

is what i meant to put

4. May 25, 2016

### rpthomps

I think you mean squared, not square root.

5. May 25, 2016

### pennywise1234

yes, sorry

6. May 26, 2016

### haruspex

You got 2.2 what? You don't know the velocity, so how can you get the velocity components?

7. May 26, 2016

### pennywise1234

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. May 26, 2016

### rpthomps

The initial velocity cannot be 0. Otherwise, with gravity being the only accelerator the projectile would go down.

9. May 26, 2016

### rpthomps

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. May 26, 2016

### haruspex

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. May 26, 2016

### pennywise1234

I am trying to find displacement though

12. May 26, 2016

### haruspex

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.