Virtual Lab: Momentum & Collisions
Name:
In this virtual experiment you will study the momentum of two carts with various masses. The
carts will be pushed toward each other, and will then undergo either elastic or inelastic
collisions. You will find the mass and velocity of the carts prior to and following the collision in
order to compare the momentum before and after the carts move apart.
Learning Outcomes (Students will be able to…):
 apply quantitatively the law of conservation of momentum to one-dimensional collisions
and explosions
 determine which laws of conservation, momentum, and energy are best used to analyse
and solve particular real-life problems in elastic and inelastic interactions
□ (1) Does not meet
outcome
□ (2) Meet outcome
with assistance
□ (3) Meets outcome
□ (4) Meets outcome
with minimal or no
assistance
with in-depth
understanding
Purpose:
 How will the momentum of the carts change before and after the collision?
 What differences can you expect between inelastic and elastic collisions?
Procedure:
1. The virtual lab can be found at Mr. Jennings
Home Page (Physics 11 page  Momentum &
Collisions Virtual Lab) or http://www.walterfendt.de/ph11e/collision.htm. You will see a
screen that is yellow and green. The yellow
screen contains a virtual table on which you
can cause carts of varying masses and with
varying velocities to collide. The green screen
allows you to control the initial conditions of
the collisions. Spend some time playing with
the virtual lab to become familiar with it.
2. Prepare two data tables on a separate piece of paper. Table 1 is for trials in which the
collisions are elastic. Label columns: Trial, m1 (kg), m2 (kg), v1,i (m/s), v2,i (m/s), v1,f (m/s),
and v2,f (m/s). In the first column, number trials 1 through 10.
Table 2 is for trials in which the collisions are inelastic. Label columns: Trial, m1 (kg), m2
(kg), v1,i (m/s), v2,i (m/s), and vf (m/s). In the first column, number trials 1 through 10.
3. Make sure the Elastic collision radio button on the right side of the screen in the green
field is chosen. Also make sure that the Velocity radio button at the bottom of the green
field is chosen.
4. Start with the default setting: m1 = 0.5 kg, v1,i = 0.2 m/s, m2 = 0.5 kg, and v2,i = 0 m/s. Click
the yellow Start bar. Observe the carts collide.
5. Press the blue reset button. Change the mass of one of the carts by typing in a number in
one of the white boxes labeled Mass. Repeat the experiment. Change the mass of the other
cart, and repeat the experiment. Change the initial velocities of both carts, and repeat the
experiment. Notice that positive movement is to the right and negative movement is to the
left. Continue changing initial conditions until you have tried at least ten different types
of initial conditions. You might want to try to make the carts behave in different ways like
both stopping after the collision or both moving in the same direction after the collision.
Be careful to note that the initial values you input are accepted by the virtual laboratory.
If the carts will not collide given your choices, the laboratory will return to default
settings.
6. Press the Inelastic collision radio button on the right side of the screen in the green field.
Make sure that the Velocity radio button at the bottom of the green field is still chosen.
7. Copy the initial conditions that you used to study elastic collisions, in your second data
table. Repeat the trials for inelastic conditions. Record the values of vf in your second data
table.
Calculations
1. For each trial under elastic conditions, calculate the momentum of each cart before the
collision and after the collision by multiplying its mass by its velocity. Remember that
velocity and momentum are vectors, so the sign of the value is important in your
calculations.
2. For each trial under elastic conditions, calculate the kinetic energy of each cart before the
collision and after the collision by using the formula: Ek = ½ mv2. Remember that kinetic
energy is a scalar, so the sign of the value is not important in your calculations. The ‘v’
stands for speed. You may want to add columns to your data tables or build new
tables for these calculations.
3. For each trial under elastic conditions, find the total momentum of the two carts before
the collision and after the collision.
4. For each trial under inelastic conditions, find the momentum of each of the two carts
before the collision.
5. For each trial under inelastic conditions, find the total momentum of the two carts before
the collision.
6. For each trial under elastic conditions, find the total kinetic energy of the two carts before
the collision and after the collision.
7. For each trial under inelastic conditions, find the total kinetic energy of the two carts
before the collision and after the collision.
Discussion Questions
1. In this situation, conservation of velocity would mean that the total velocity for both carts
is the same after the collision as it was before the collision. Is velocity conserved in elastic
conditions? Is it conserved in inelastic conditions? Support your answer with data from
your experiment.
2. Based on your data, is momentum conserved in elastic conditions? Support your answer
with data from the experiment.
3. Based on your data, is momentum conserved in inelastic conditions? Support your answer
with data from the experiment.
4. Based on your data, is kinetic energy conserved in elastic conditions? Support your answer
with data from the experiment.
5. Based on your data, is kinetic energy conserved in inelastic conditions? Support your
answer with data from the experiment.
6. How would performing this experiment in a hands-on laboratory affect the data you
collected? What sources of error could you expect in real-life conditions that you could
neglect in a virtual setting?