A question of interpretation

Alright. I am smart about some things and dumb about others. I need someone smart in math and physics to help me out.
I know that force=mass*acceleration.
My question is, how much force is involved when a kid throws a 4 oz. rock at a vehicle travelling 45 MPH. Assuming the kid is the standard skinny iraqi kid, and throws like a girl, he's mybe throwing what, 30 MPH? Assume the angle from thrower to object is 30 deg. I'll try to draw it.

X (iraqi kid)


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Here's what I am getting at. Would the rock hitting an exposed person have deadly force--could it kill you?

Now, the only real argument I've heard is that is that the only person who is exposed is the gunner, and he's supposed to travel down inside the gun shield, so as not to get hit. If that's the case, then a guy standing by the side of the road shooting an AK is not using deadly force, even if the bullets are hitting the truck, because the truck's armor will stop 7.62mm ammunition.

Really, I want to know how much force could that rock hit the truck (or an exposed person) with?

Chuck (The stupid state-schooled guy)

The reason for this exercise lies in the comments section.