Soccer 'Heading': Calculating Impulse of a Ball

[nicknaq]

Homework Statement

Recent studies have raised concern about `heading' in youth soccer (i.e., hitting the ball with the head). A soccer player `heads' a size 4 ball, deflecting it by 38.0 deg, but keeping its speed of 19.60 m/s constant. A size 4 ball has a mass of approximately 0.302 kg. What is the magnitude of the impulse which the player imparts to the ball?
CORRECT ANSWER: 3.85 kg*m/s

Homework Equations

p=mv
draw a vector diagram

The Attempt at a Solution

I drew a vector diagram with the vector p=mv=5.9 going in the +x direction. I then drew the deflection of 38 degrees going in the negative and positive direction.

Ok so I found the hypotenuse (the redirection) to be 7.48.

Then I thought it would be 7.48-5.9, but alas, nope.

Any help?

 

[nicknaq]

bumpidity

 

[collinsmark]

bumpidity

The impulse on a given object is the change in momentum on that given object.

But don't forget, momentum is a vector and needs to be treated as such.

I drew a vector diagram with the vector p=mv=5.9 going in the +x direction. I then drew the deflection of 38 degrees going in the negative and positive direction.

Ok so I found the hypotenuse (the redirection) to be 7.48.

No, that's not quite right. The problem statement says, "...deflecting it by 38.0 deg, but keeping its speed of 19.60 m/s constant."

So the hypotenuse of momentum after the collision is still (0.302 [kg])(19.60 [m/s]). The hypotenuse is unchanged in magnitude.

However, what did change is the momentum vector's direction. So allow me to ask,

• What is the momentum vector after the collision?
• What is the momentum vector before the collision?
• What is the difference between the two (i.e. the change in momentum)? [Hint: this involves subtracting vectors, not scalars. ]
• What is the magnitude of this change?