# Football kick projectile problem

1. Sep 30, 2005

### nrc_8706

a place kicker must kick a football from a point 35m from the goal, and the ball must clear the crossbar, which is 3.05m high. When kicked, the ball leaves the ground with a speed of 26m/s at an angle of 55 degrees to the horizontal. By how much does the ball clear or fall short of clearing the crossbar?

i found time by using Vy=Vyo-gt which is 4.826s.
what do you do next? Can you use range?

2. Sep 30, 2005

### Integral

Staff Emeritus
Please show us your work. Over 4 seconds seems like a long time to travel 35m.

3. Sep 30, 2005

### nrc_8706

projectile

vy=vyo-gt. vy=0 cause is at the highest point or is it vy?
then i divided vosinangle/9.8=21.298/9.8=2.17326s

total time is 2(21.298)/9.8=4.34653s

4. Sep 30, 2005

### Integral

Staff Emeritus
What are you looking for?

5. Sep 30, 2005

### Grogs

You've solved for the time it takes the football to reach it's maximum height and the time it takes until the ball strikes the ground. Your numbers look correct, but they won't help you solve the problem.

You're not interested in how far or how high the ball travels. You're interested in a certain point in the ball's trajectory. Try setting up all 4 equations (x,y,vx,vy) for that point and see if that helps.

6. Sep 30, 2005

### Integral

Staff Emeritus
Can you figure out how to answer these questions.

How long does it take the ball to cover the distance to the goal post? What information do you have that could get you this?

How high is the ball at that time?

You are computing how long it takes to reach the peak of motion and how long it takes to return to the ground, but those are not questions asked by the problem. ( just noticed grogs post, I am repeating what he had to say... sorry.