**Law of Conservation of Momentum LCM
**

**Materials:**
air track, two gliders, two photogates, masses, neodymium
magnets, clay

**Procedures**

1. Set up the air track and photogates using
neodymium magnetic bumpers on the gliders to provide a nearly
elastic collision. Be
sure the air track is level, otherwise an external force (mgSin2)
is present.

2. Mass m_{1} and m_{2}. Record the lengths L1 and L2 of each glider
(usually 0.01 m) through the photogate.

3. Set both photogate timers to GATE mode, then
press the RESET button.

4. Place glider_{2} at rest between the
photogates. Give
glider_{1} a* gentle* push towards glider_{2}.

[**IMPORTANT**: the collision must occur after glider_{1}
has passed completely through photogate_{1}. After the
collision, the gliders must be fully separated before either
glider interrupts a photogate.]

Record four time measurements:

t_{1i}
the time that glider_{1} blocks photogate_{1}
before the collision.

t_{2i}
the time that glider_{2} blocks photogate_{2}
before the collision (zero if glider_{2} starts at rest).

t_{1f}
the time that glider_{1} blocks photogate_{1}
after the collision (zero if it stops between the photogates.)

t_{2f}
the time that glider_{2} blocks photogate_{2}
after the collision.

5. Repeat Steps 3 and 4 for one more situation
when glider_{2} has a greater mass than glider_{1}.
If glider_{1} bounces back, you will need to
determine the t_{1f }.

6. Add a sesame seed-sized slice of silicated
soil to one of the gliders for the inelastic collision.

7. Set both photogates to GATE mode, and press
the RESET button.

8. With glider_{1} as the *only*
glider with a timing interrupter,
place glider_{2} at rest between the two
photogates. Give
glider_{1} a gentle push towards glider_{2},
recording the following times:

t_{1i}
the time that glider_{1} blocks photogate_{1}
before the collision.

t_{1f}
the time that glider_{1} blocks photogate_{2}
after the inelastic collision.

9. Repeat Steps 7 and 8 for one more situation of
different mass on either glider.**
**

**Analysis**

1. For each time measurement, calculate the
corresponding glider velocity.

2. Use your measured and calculated values to
calculate p_{i} and p_{f}. for all collisions
performed. Be care of +/- velocities and +/- momenta.

3. State the LCM.
Was momentum reasonably conserved? What are some sources of
error in this lab?

4. Define the terms *elastic* and *inelastic*
collisions.