This preview shows pages 1–3. Sign up to view the full content.
Lesson 4: 2D Collisions
We now need to turn our attention towards questions involving objects that collide in two dimensions
(2D).
●
In the previous section we were looking at only linear collisions (1D), which were quite a bit
simpler (mathematically) to handle
.
●
Now we need to figure out some ways to handle calculations in more than 1D.
○
You actually learned about this in Physics 20 in the vectors section.
First, let’s look at drawing some diagrams of some common collisions, then we’ll worry about the
calculations…
Example 1
:
Sketch
a diagram that represents the collision between two moving pool balls (of equal
mass) that strike each other with an angle of 30
°
between them. They do not stick together.
We need to show what happens before and after the collision.
●
So far this is just a rough sketch, since we weren’t told anything about their velocities or
the angle that they traveled away at.
●
All that we’re doing at this point is showing that we know that the balls should move off
in directions similar to the ones shown here.
Example 2
:
Sketch
a diagram that represents the collision between a moving pool ball that strikes a
stationary pool ball. They move off with an angle of 60
°
between them.
10/28/2009
© studyphysics.ca
Page 1 of 6 / Section 9.4
Illustration 1: Collision between two moving balls
After
Before
30
o
Illustration 2: Collision between one moving and one stationary
ball
After
Before
60
o
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentIn examples like this you will often see that the question refers to the collision as “
glancing
.”
●
This simply means that the objects do
not
hit head on. If they did hit head on then the collision
would be 1D, not 2D.
Now we need to start looking at some questions with calculations.
●
Some people are more comfortable doing these questions using components, others like using
cosine and sine laws.
●
Since not everyone knows cosine and sine laws, we'll only use components in the following
examples.
Example 3
: A 1.20 kg
red
ball moving to the right at 17.1m/s strikes a stationary 2.31 kg
blue
ball. If
the final velocity of the
red
ball is 13.5m/s at 23.0
°
above the horizontal,
determine
the final velocity
of the
blue
ball.
A sketch is always a good idea, even if you're not asked for one.
This is the end of the preview. Sign up
to
access the rest of the document.
 Fall '08
 Staff

Click to edit the document details