CONSERVATION OF LINEAR MOMENTUM– MOMENTUM TRANSFER
Introduction: Linear momentum is defined as the product of the mass and the velocity of an
object,
p = mv
where v is the instantaneous velocity of the object. The Law of Conservation of
Momentum states that The total linear momentum of an isolated system remains
constant if there is no net external force acting on the system. In other words:
Total final momentum of system = Total initial momentum of system
Pf = Pi
mfvf = mivi
Objective: To demonstrate Conservation of Momentum
1. Momentum can transfer from one object to another.
2. Momentum can pass from one object, through a second, into a third.
3. The total momentum in an isolated system is conserved
Materials: Two Yardsticks, Tape, Six steel balls
Procedure:
1. Tape the two yardsticks to a tabletop so they are parallel and about ½ inch apart
(depending on the size of the steel balls). You want the balls to be able to rest
on the meter sticks like a track, without touching the table.
2. Put 2 steel balls in the middle of the sticks, on the ‘track’, a few inches apart.
3. Flick a ball so that it rolls and hits the other one. Observe and note what
happens.
4. Now put two balls on the track so they touch, and a third several inches away.
Flick the single ball into the other two. Observe and note what happens.
5. Repeat the procedure with the remaining configurations and observe and note
what happens.
Configurations:
(a) One ball into one stationary ball
(b) Two balls into two stationary balls
(c) Three into three
(d) Two into three
(e) Your own configuration
Questions
Configuration A: One ball rolled into one ball
What did you observe?
Was momentum conserved? Explain how your observations support your answer.
How does the initial mass of the moving objects compare with the final mass of the moving
objects?
How does the initial velocity of the moving objects compare with the final velocity of the
moving objects?
Configuration B: Two balls rolled into two balls
What did you observe?
Was momentum conserved? Explain how your observations support your answer.
How does the initial mass of the moving objects compare with the final mass of the moving
objects?
How does the initial velocity of the moving objects compare with the final velocity of the
moving objects?
Configuration C: Two balls rolled into three balls
What did you observe?
Was momentum conserved? Explain how your observations support your answer.
How does the initial mass of the moving objects compare with the final mass of the moving
objects?
How does the initial velocity of the moving objects compare with the final velocity of the
moving objects?
Configuration D: Three balls rolled into two balls
What did you observe?
Was momentum conserved? Explain how your observations support your answer.
How does the initial mass of the moving objects compare with the final mass of the moving
objects?
How does the initial velocity of the moving objects compare with the final velocity of the
moving objects?
Configuration E: Design your own configuration
Explain your configuration. Draw a picture.
FIRST, What do you expect to happen? Explain your reasoning.
SECOND, try it out. What did you observe?
Was momentum conserved? Explain how your observations support your answer.
How does the initial mass of the moving objects compare with the final mass of the moving
objects?
How does the initial velocity of the moving objects compare with the final velocity of the
moving objects?
Final Question
If three moving balls hit two stationary balls, why wouldn’t the two continue to roll, just at a
faster pace to keep mfvf = mivi? (This isn’t something we’ve covered, but jot down some
thoughts.)