Collisions & Conservation of Momentum. There are 2 types of collisions that can occur :. Elastic Collisions Inelastic Collisions. When two object collide with each other and bounce apart without sticking to each other. When two objects collide with each other
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Collisions & Conservation of Momentum
Elastic CollisionsInelastic Collisions
When two object collide with each other and bounce apart without sticking to each other.
When two objects collide with each other
And stick or stay together after the collision.
Think about two or more pool balls striking each other. After the collision, the balls are separate from each other just as they were before the collision. This is an elastic collision.
Think about a baseball colliding with a catcher’s mitt. After the collision the ball and mitt are still in contact with each other. This is an inelastic collision.
Most collisions in life are a combination of both Elastic and Inelastic collisions.
Try to put these collisions in one of the following categories:
Mixture of both Elastic AND Inelastic
A soccer player’s foot colliding with a soccer ball.
Two cars colliding head-on at high speed.
A bowling ball striking the pins.
A ball of clay thrown against a concrete wall.
A skydiver WITHOUT a parachute colliding with the ground below.
A snowball thrown at a stop sign.
A rubber ball thrown against a concrete wall.
A football defensive linebacker tackling a running back.
This means that the momentum lost by one object will be gained by another.
The TOTAL momentum of the two objects will ALWAYS be the same after the collision as before the collision.
Let’s consider another example:
A 100kg defensive lineman running at 4m/s tackles an 80kg quarterback standing in the pocket. After the tackle the lineman slows down to 1m/s.
When you solve Conservation of Momentum problems,
It is good to set up a chart like this:
Before the Collision
TOTAL momentum BEFORE
These have to be
the SAME !
After the collision
TOTAL momentum AFTER
Whenever two or more objects collide, the TOTAL momentum of the objects cannot change !
Now, the chart will help you remember how you will use Conservation of Momentum to solve problems.
But, here is an easier equation that you can use on a daily basis:
m1*v1i + m2*v2i = m1*v1f + m2*v2f
Try problems on your own in your notebook:
Two objects collide. Object 1 has a mass of 50kg and is initially traveling at 6m/s. Object 2 has a mass of 20kg and is initially traveling at 8m/s. After they collide, object 2 is now traveling at 11m/s. How fast does object 1 travel after the collision?
An accident investigator analyses a collision of a motorcycle and a car. He sees that after the collision the motorcycle (mass=550kg) moved at 10m/s and the car(mass=1000kg) moved at 8m/s. A witness says that before the accident the motorcycle was traveling at 7m/s. If you are the investigator, how fast do you think the car was traveling BEFORE the accident?