- #1
HRubss
- 66
- 1
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
vfinal2 = vinitial2 +2a(yfinal-yinitial)
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/s2. With that information, I set yinitial = 0m and yfinal = 3m. From there, I used the equation above to find vinitial (rearranging the formula to have vinitial2 = vfinal2-2a(yfinal-yinitial) , (numbers plugged in.. vinitial2 = (0m/s)2 -2(-9.81m/s2)(3m-0m)) and got vinitial = 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.