What Angle Maximizes Air Time for a 34.6m Football Punt?

[mh_99]

Homework Statement

A football punter can punt a maximum range of 40.8 m. If he instead wants to punt only 34.6 m, but maximize the time the ball is in the air, at what angle from the horizontal should he kick the ball, and how long will it stay in the air if he hits it perfectly? (neglect air resistance) Assume he can kick the ball with the same force every time.

Homework Equations

• R = (u²sin 2θ) / g
• R_max = u²/g

The Attempt at a Solution

I used the above equations to solve the problem but I'm getting 29.0 degrees and 1.98 seconds. When I try to submit my answers says it's wrong. Do I have the right sig figures or it just something wrong on my calculations

 

[TSny]

Hello and welcome to PF!

Consider the possibility that there might be more than one mathematical solution to your equations. In particular, the inverse sine function on your calculator probably only gives you the "principal value". For example, my calculator tells me sin^-1(0.5) is 30 degrees. It misses the fact that sin(150^o) is also 0.5.

 

[magoo]

Why don't you show your calcs.

What if he kicked it at 90 degrees?