Application to particle physics And the last one problem. You will solve it using those ideas. At least it is physics problem. Here is a wall and a line, represented by the equation x−2y=1. A particle then enters the picture. When a particle collides with the wall, it bounces off. So, bouncing off a wall could be like a projectile or you could think of a light ray. When something bounces off a wall, the angle of incidence (the angle at which it hits the wall) is equal to the angle of reflection (the angle from which it bounces back). If the ball has no friction, its speed will be the same when it bounces off as when it entered. The incoming velocity, V incoming, is equal to the outgoing velocity, V outgoing. The problem you will address is given the incoming velocity and the equation of the wall, determine the velocity of the particle after it bounces off. The task is to find the outgoing velocity. Consequently, this is another example of a real world problem. The key to this problem is to break vectors into components in one direction or perpendicular to the vector's direction. So in this case, it helps to write this as a piece that is tangent to the wall, and a piece that is normal to a wall.