HTML and CSS Reference
In-Depth Information
vx = 10
vx = -6
mass = 2
mass = 3
Figure 11-2.
A one-dimensional collision
As you can see, the objects have different sizes, different masses, and different velocities. The velocities
are represented by arrows coming out from the center of each ball—these are vectors. A velocity vector
points in the direction of the motion and its length indicates the speed.
The one-dimensional example is simple because both velocity vectors were along the x axis, so you can
add and subtract their magnitudes directly. But, take a look at Figure 11-3, which shows two balls colliding
in two dimensions.
Figure 11-3.
A two-dimensional collision
Because the velocities are in completely different directions, you can't just plug the velocities into the
momentum-conservation formula. So, how do you solve this?
You start by making the second diagram look a bit more like the first by rotating it. First, figure out the
angle formed by the positions of the two balls and rotate the entire scene—positions and velocities—
counterclockwise by that amount. For example, if the angle is 30 degrees, rotate everything by -30. This is
exactly the same thing you did in Chapter 10 to bounce off an angled surface. The resulting diagram looks
like Figure 11-4.
