What is the change in momentum for a baseball striking a fence at a 45° angle?

[meganw]

Homework Statement

A 138 g baseball, moving along the x-axis with speed 21.0 m/s, strikes a fence at a 45° angle and rebounds along the y-axis with unchanged speed. Give its change in momentum using unit vector notation.
_____ i + ______ j kg·m/s

Homework Equations

Momentum = (mass)(velocity)

The Attempt at a Solution

Honestly, our teacher hasn't taught us momentum, but gave us this assignment anyways. I'm really very confused. Any help would be great. :)

 

[Mindscrape]

Really all you need to use is conservation of momentum. The ball is going all in the x direction to start with, and then it is going all in the y direction. Figure out the difference between the components.

 

[qspeechc]

This has nothing to do with momentum- the problem is one of vectors, ie. a maths problem.

Draw or write the vector representing the initial and final momentae, then find the vector you need to add to the initial momentum vector to get the final momentum vector.