Name:
Date:
Lab 3: Momentum - Virtual Simulations
Visit the website: http://phet.colorado.edu/en/simulation/collision-lab, or open the application on
the USB drive. Use the following instructions to help you explore the simulation and familiarize
yourself with the controls:
1. Change the setting between 1 and 2 Dimensions and notice what
changes.
2. Turn on velocity vectors. Drag the green arrow attached to one of
the balls. What happens to the total kinetic energy of the system (lower
left corner of screen)?
3. Turn on momentum vectors. Drag the green velocity arrows. What
happens to the yellow arrows? Why?
4. Turn off the Reflecting Border and play the simulation. What
happens?
5. Turn on the Momenta diagram, and run the default simulation.
What do you think the pink arrow in this new window represents?
6. Move the elasticity slider all the way to the left, and run the default
simulation. What happens during the collision?
7. Move the elasticity slider somewhere in the middle, and run the default simulation. What
happens?
8. With momentum vectors turned on, drag the mass sliders. What happens to the yellow arrows?
Why?
9. With momentum and velocity vectors turned on, click on more data. Adjust the green arrows
and notice what happens to the data values. Drag one of the balls around the screen and notice
what happens to the data values.
10. Adjust the time rate slider all the way to the left, then all the way to the right. What happens?
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For the following questions you must create the scenario that is described, make a prediction about
what you expect to happen during the collision, and then run the scenario to observe and record the
actual results.
Make sure that velocity and momentum vectors, show paths, and momenta diagram are turned on,
reflecting border and center of mass are turned off. Include the dotted line paths in your diagrams.
1. A 1-dimensional, 100% elastic collision between 2 balls of equal mass and equal velocity.
Diagram: Before
Ball
After (Predicted)
Mass
V
-
-
P
After (Observed)
V’
P’
Predict
Observe
-
-
Predict
Observe
1
2
System
2. A 1-dimensional, 100% elastic collision between 2 balls of equal mass but different velocity.
Diagram: Before
Ball
After (Predicted)
Mass
V
-
-
P
After (Observed)
V’
P’
Predict
Observe
-
-
Predict
Observe
1
2
System
3. A 2-dimensiaonl, 100% elastic collision between 2 balls, one ball is stationary, the 2nd ball is
approaching from some angle.
Diagram: Before
Ball
After (Predicted)
Mass
V
-
-
P
After (Observed)
V’
P’
Predict
Observe
-
-
Predict
Observe
1
2
System
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4. A 2-dimensional, 0% elastic (inelastic) collision between 2 balls, one ball is stationary, the 2nd
ball is approaching from some angle.
Diagram: Before
Ball
After (Predicted)
Mass
V
-
-
P
After (Observed)
V’
P’
Predict
Observe
-
-
Predict
Observe
1
2
System
5. Create a scenario of your own choosing, that is different from all of the above. Be sure to write
the scenario details below.
Scenario:
Diagram: Before
Ball
After (Predicted)
Mass
V
-
-
P
After (Observed)
V’
P’
Predict
Observe
-
-
Predict
Observe
1
2
System
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1-DIMENSIONAL COLLISIONS
6. Fill in the following table by calculating the missing values, using the formulas we have for
conservation of momentum, and kinetic energy. Show your calculations on a separate sheet of
paper.
Remember, for elastic collisions:
Ek = Ek’
½m1v12 + ½m2v22 = ½m1v1’2 + ½m2v2’2
a. Elastic Collisions:
Prepare the simulation with these settings for each of the following scenarios:




1-Dimensional
Elasticity = 100%
Velocity Vectors, Momentum Vectors, Show Paths, and Momenta Diagram = ON
Reflecting Border, and Center of Mass = OFF
M1
M2
V1
V2
Psystem
V1’
V2’
Psystem’
(kg)
(kg)
(m/s)
(m/s)
(kgm/s)
(m/s)
(m/s)
(kgm/s)
1
1.20
1.20
+1.50
-1.80
-1.80
2
2.40
4.80
+1.30
0.0
-.433
3
2.50
3.90
4
5.10
1.00
#
.850
0.900
11.5
2.06
4.60
-4.60
b. Inelastic Collisions:
Prepare the simulation with these settings for each of the following scenarios:




1-Dimensional
Elasticity = 0%
Velocity Vectors, Momentum Vectors, Show Paths, and Momenta Diagram = ON
Reflecting Border, and Center of Mass = OFF
M1
M2
V1
V2
Psystem
M12
V12’
Psystem’
(kg)
(kg)
(m/s)
(m/s)
(kgm/s)
(kg)
(m/s)
(kgm/s)
1
1.20
1.20
+1.50
-1.80
2
2.40
4.80
+1.30
3
1.50
5.50
+3.20
4
2.50
#
1.00
7.00
+0.80
0.0
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2-Dimensional Collisions
7. Prepare a two-dimensional inelastic collision (0% elastic) involving two balls of different mass
and different velocities, which are directed at some angle towards each other.
a. Draw vector diagrams (right-angle triangles) for the initial velocity of each ball BEFORE
the collision. You must calculate the angle using the x and y components of the velocity,
which are found in the more data section of the simulator.
b. Calculate the final velocity and final momentum of the system. Show your calculations on a
separate sheet of paper.
v12’ = ______________________________________
p12’ = _______________________________________
c. Draw a vector diagram for the final velocity of the system AFTER the collision.
d. Check your answer by running the simulation. Were you correct? ___________________.
e. Draw the Momenta Diagram for the system BEFORE and AFTER the collision.
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8. Prepare a two-dimensional 100% elastic collision involving two balls of different mass and
different velocities, which are directed at some angle towards each other.
a. Draw vector diagrams (right-angle triangles) for the initial velocity of each ball BEFORE
the collision. You must calculate the angle using the x and y components of the velocity,
which are found in the more data section of the simulator. Do not run the simulation yet!
b. Draw a diagram that predicts the motion of the balls after the collision
c. Calculate the final velocity and final momentum of each ball, and the system after the
collision. Show your calculations on a separate sheet of paper. Do not forget the angles!
v1’ = ______________________________________
p1’ = _______________________________________
v2’ = ______________________________________
p2’ = _______________________________________
psystem’= __________________________________
d. Draw a vector diagram for the final velocity of each ball AFTER the collision.
e. Check your answer by running the simulation. Were you correct? ___________________.
f.
Draw the Momenta Diagram for the system BEFORE and AFTER the collision.
Page 6