How Do You Calculate the Average Force Applied to a Basketball with a Kick?

[jghappel]

A 0.7 kg basketball is rolling by you at 3.5 m/s. As it goes by, you give it a quick kick perpendicular to its path. Your foot is in contact with the ball for 0.003 s. The ball eventually rolls at an angle of theta = 30 degrees from its original direction.
Determine the magnitude of the average force you applied to the ball.

Not sure how to do this, I am using the momentum principle and its not working

 

[Iceclover]

whats not working about it? what answer did you come up with?