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## Homework Statement

A football is kicked from the ground at an angle of 40° to the ground. It travels 42m and just passes over the goal post which is 3m high. What was the inital velocity of the football?

## Homework Equations

v

_{final}

^{2}= v

_{initial}

^{2}+2a(y

_{final}-y

_{initial})

## The Attempt at a Solution

Assuming that the football from the start to finish creates a symmetric parabolic line, I realize that when the football reaches it's highest point, it stops gaining velocity and has an acceleration of -9.81m/s

^{2}. With that information, I set y

_{initial}= 0m and y

_{final}= 3m. From there, I used the equation above to find v

_{initial}(rearranging the formula to have v

_{initial}

^{2}= v

_{final}

^{2}-2a(y

_{final}-y

_{initial}) , (numbers plugged in.. v

_{initial}

^{2}= (0m/s)

^{2}-2(-9.81m/s

^{2})(3m-0m)) and got v

_{initial}= 4m/s in the y direction. Knowing that velocity in the y direction = velocity(sin(Θ)), rearranging the function to yvelocity/(sin(Θ)) = velocity, I got 6.2m/s as initial velocity of the football. I appreciate any feedback.