# Projectile Motion football kick

Can someone work show me how to work this? I am very confused.
1. A place kicker must kick a football from a point 36.0 m (about 40.0 yd) from the goal, and the ball must clear the crossbar, which is 3.05 m high. When kicked, the ball leaves the ground with a speed of 31.0 m/s at an angle of 50° to the horizontal.What is the vertical component of velocity of the ball at this time? (Assume the positive direction is upward.)

Last edited:

Hurkyl
Staff Emeritus
Gold Member
Don't multiple post.

I have a better idea -- why don't you tell us how you worked the problem, and we can tell you where you went wrong, if anywhere?

Sorry. First time in the threads

I got 13.7 for the m for the change in X. I dont no where to go past that. What should I do.

Vi= 31
Angle-50
X=36
Y=13.7? I think. Where do I go from there? Thanks

Is it Vx=Vxi=Vxf so is it 31?

Tom Mattson
Staff Emeritus
Gold Member
chriszollman said:
What is the vertical component of velocity of the ball at this time? (Assume the positive direction is upward.)

At what time? Initially? At the crossbar? Some other time?

If it's the first one, then this problem is a piece of cake. You can ignore all the stuff about the distances and just use the info on the initial velocity.

this is a toughy!

yeah i tried really hard on this problem and i cant work it out. i think it has to do with the cosin or sin of the angle because it makes a right triangle, let me know if anyone figures anything out.

Its the one on the cross bar

Tom Mattson
Staff Emeritus
$$x=v_i\cos(\theta)t$$.
Then you've been asked for the vertical component of the velocity. That would be the y-component. You have an equation for the $v_y$ as a function of time. You will need to use that to answer the question.