Need help finding what formula to use?

[maegenr8]

Homework Statement

A tennis player hits a ball at ground level, giving it an initial velocity of 26 m/s^2 at 54 degrees above the horizontal. How high above the ground does the ball go?

Homework Equations

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The Attempt at a Solution

I found out the horizontal velocity, which is 15.3 and the vertical velocity which is 21.0

 

[Jebus_Chris]

In projectile motion the highest point occurs right in the middle when the vertical speed is zero.

 

[maegenr8]

Yeah, I understand that. What formula would I use to actually find the height though?

 

[Jebus_Chris]

$$v^2=v_o^2+2a\Delta y$$

 

[maegenr8]

So if at the highest point there is a vertical speed of zero, would I put zero in for v^2? 26 for initial velocity and -9.8 for acceleration?

 

[Jebus_Chris]

Yes.

 

[maegenr8]

the answer is 22.6, but when i do that I get 34.49

 

[maegenr8]

ohh... I think I needed to put in the vertical velocity which was 21.0 instead. Then that formula works.