Easy "Ballin'" achievement
Select Green Team Stage 1 Race 4 and follow the snowball downhill. It will eventually jump to your right side, back to the left, then to the right again. Watch where it drops down and crosses the road back to the left. It will cross close to the road just where you go over a jump. This is the location you need to be at to get hit. Restart and make sure you get to that location just before the snowball arrives.