# Finding maximum Height

## 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 ^^

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

is what i meant to put

I think you mean squared, not square root.

yes, sorry

haruspex
Homework Helper
Gold Member
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?

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

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

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?

haruspex
Homework Helper
Gold Member
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?

I am trying to find displacement though

haruspex