# Homework Help: Ballistics - Find magnitude of force on a kicked ball

1. Sep 16, 2006

### tyfiem

a ball of mass 0.2 kg, initially at rest, is kicked directly toward a fence from a point 20m away. The velocity of the ball as it leaves the kicker's foot is 20m/s at angle of 40º above the horizontal ground. The top of the fence is 4m high. THe kicker's foot is in contact with the ball for 0.05s. The ball hits nothing while in flight and air resistance is negligible. The acceleration due to gravity is 9.8m/s^2. Determine the magnitude of the average net force exerted on the ball during the kick. Answer in units of N.

I need help with this question. it is quite confusing and I'm stuck..

I think the equation: cos(38) x 17m/s = 1/2 a t^2 comes in somewhere in this question, but i don't know how it fits into this question. I'm seriously stuck D: can anyone help me? thanks in advance!

Last edited: Sep 16, 2006
2. Sep 17, 2006

### Andrew Mason

What is the momentum of the ball when it leaves the foot? How is the momentum related to the impulse given to the ball (Force x time)?

The angle, fence height or gravity is not relevant to this question.

AM