Momentum
Objectives- describe what momentum is, how momentum is conserved and how momentum is
calculated.
When coaches talk about momentum, it is likely they have it just a little, well, wrong. A team
may be moving forward, catching back up, getting farther ahead- all related to speed in a way, but not
gaining momentum. Now if a football coach says his middle linebacker or defensive end has
momentum, the coach is correct. Momentum is more than speed. Momentum also includes the mass
of the object. To calculate momentum multiply the mass times the velocity (p = m x v). Even though the
formula says v (velocity) we will be using the speed. The label for momentum is kg x m/s.
When objects collide, the momentum of one object can be transferred to another. The amount
of momentum lost by one object is gained by the other. This idea is called the Law of Conservation of
Momentum. Think of the game of pool. At first, none of the balls have any momentum- none of them
are moving. The cue ball gains momentum when it is hit. Let’s say it is hit pretty hard so it has a lot of
momentum and it hits the other 15 balls. The cue ball stops- it lost its momentum, but the 15 begin to
move. They gained momentum. None of the 15 moved as fast as the cue ball did. Let’s make up some
numbers to show what happened. Image the cue ball had a momentum of 15kg x m/s. It stopped and
all the momentum went to the other 15 equally. So each of the 15 balls had a momentum of 1kg x m/sa total of 15kg x m/s. In reality, not all the balls would probably have the same momentum. But if the
cue ball lost all of its momentum, then the total the 15 have would be 15kg x m/s. Let’s say the cue ball
only hit one of the 15 and the cue ball kept moving. It started with a momentum of 15kg x m/s, but
ended up with a momentum of 5kg x m/s. How much momentum did the one ball gain? The
momentum gained would be 10kg x m/s. The total momentum before and after the collision was 15kg x
m/s.
Define momentum
What is the formula for calculating momentum?
What is the label for momentum?
What is the law of conservation of momentum?
How are inertia, force and momentum alike? Different?
A linebacker has a mass of 125kg and run 40meters in 4.4 seconds. How much momentum does he
have?
Which has more momentum a fast moving squirrel or an elephant standing still? Explain.
Which has more inertia a fast moving squirrel or an elephant standing still? Explain
Often debated in hunting magazines is which is better to use a fast light weight arrow or a slower
heavier one. The light arrow has a mass of 125g and travels at 120m/s. The heavier arrow weighs 155g
and travels at 105m/s. Which would be better? Why did you choose the answer you did?