In the previous two sections,
we used the conservation of momentum
to analyze two cars in a crash.
All of these were rearend collisions,
in which one car hit another moving in the same direction.
In this section, we will move to headon collisions.
In these problems, objects move in two different directions.


Before the collision...

Car A has a mass of 400 kg and is moving RIGHT with a speed of 10 m/s.

Car B has a mass of 200 kg and is moving LEFT with a speed of 5 m/s.

After the collision...

Car A is stationary.

What is the magnitude and direction
of car B's velocity?


Before the collision...

Car A has a mass of 300 kg and is moving RIGHT with a speed of 12 m/s.

Car B has a mass of 100 kg and is moving LEFT with a speed of 6 m/s.

After the collision...

Car A is stationary.

What is the magnitude and direction
of car B's velocity?


Before the collision...

Car A has a mass of 100 kg and is moving LEFT with a speed of 8 m/s.

Car B has a mass of 150 kg and is moving RIGHT with a speed of 4 m/s.

After the collision...

Car B is stationary.

What is the magnitude and direction
of car A's velocity?


Before the collision...

Car A has a mass of 30 kg and is moving RIGHT with a speed of 12 m/s.

Car B has a mass of 40 kg and is moving LEFT with a speed of 6 m/s.

After the collision...

Car A moving to the LEFT with a speed of 2 m/s.

What is the magnitude and direction
of car B's velocity?


Before the collision...

Car A has a mass of 2000 kg and is moving RIGHT with a speed of 3 m/s.

Car B has a mass of 4000 kg and is moving LEFT with a speed of 9 m/s.

After the collision...

Car A is moving LEFT with a speed of 8 m/s.

What is the magnitude and direction
of car B's velocity?


Before the collision...

Car A has a mass of 400 kg and is moving RIGHT with a speed of 5 m/s.

Car B has a mass of 200 kg and is moving LEFT with a speed of 10 m/s.

The collision is totally inelastic.

What happens after the collision?

A railroad car with a mass of 50,000 kg is moving at a speed
of 40 m/s when it smashes into a running tree trunk
moving the other way at 5 m/s with a mass of 20,000 kg.
The tree lodges in the railroad car. Nobody is injured, including the tree trunk.
What is their speed and direction after the collision?

A linebacker with a mass of 140 kg is running downfield at 9 m/s
towards a 120 kg running back running upfield with a speed of 8 m/s.
They collide, and the linebacker wraps up the running back so they stick
together.
What is their speed and direction after the collision?

A red bumper car with a mass of 200 kg is driving to the right with a speed
of 5 m/s. A blue bumper car with a mass of 200 kg is driving to the left
with a speed of 6 m/s.
They smash into each other. Each bumper car bounces back in the opposite direciton
it was moving!
If the red car has a speed of 4 m/s after the collision,
what is the speed of the blue car?

A bumper car with a mass of 200 kg is driving forward (+) really fast,
with a speed of 30 m/s.
It slams directly into a truck with a mass of 4000 kg that
is stationary and releases a loaded spring.
The bumper car bounces backwards () with a speed of 30 m/s.
The truck begins slowly rolling.
Determine the magnitude and direction of the truck's velocity
after the collision.
Answers