Name______________________________________________________Date_________________Period___
Colliding Carts- Conservation of Momentum on the Air Track
TASK
This activity is divided into two parts. In the first part, you will use the links provided to answer some
questions regarding momentum, impulse and collisions.
In the second part of the activity you will use a computer simulation of an
air track to study the conservation of momentum of elastic and inelastic collisions. You will need the software
ShockWave plug-in or Java in order to view the simulations.
Part I. Background
Momentum
http://www.physicsclassroom.com/Class/momentum/u4l1a.cfm
1. Momentum can be defined as __________________.
2. Momentum depends upon the variables _________and ________. In terms of an
equation, the momentum of an object is equal to the
________________________.
Momentum = mass • velocity
In physics, the symbol for the quantity momentum is the lower case "p". Thus, the above equation can
be rewritten as ________________________________ where m is the _______ and v is the
______________. The equation illustrates that
momentum is _________ proportional to an
object's mass and ___________ proportional to the object's velocity. The units for momentum would
be
_____________________.
3. Is momentum a vector? Why?
4. Go to Check Your Understanding and answer the three questions. Show all work when necessary.
a) Determine the momentum of a ...
i. 60-kg halfback moving eastward at 9 m/s.
ii. 1000-kg car moving northward at 20 m/s.
iii. 40-kg freshman moving southward at 2 m/s.
b) A car possesses 20 000 units of momentum. What would be the car's new momentum if …
i. its velocity were doubled.
Name______________________________________________________Date_________________Period___
Colliding Carts- Conservation of Momentum on the Air Track
ii. its velocity were tripled.
iii. its mass were doubled (by adding more passengers and a greater load)
iv. both its velocity were doubled and its mass were doubled.
c) A halfback (m = 60 kg), a tight end (m = 90 kg), and a lineman (m = 120 kg) are running down
the football field. Consider their ticker tape patterns below.
i. Compare the velocities of these three players.
ii. How many times greater is the velocity of the halfback and the velocity of the tight end
than the velocity of the lineman?
iii. Which player has the greatest momentum? Explain.
Momentum and Impulse Connection
http://www.physicsclassroom.com/Class/momentum/U4L1b.cfm
5. Combine Newton’s 2nd Law and the definition for acceleration to derive an expression that explains
the momentum/impulse connection.
6. The physics of collisions are governed by the laws of momentum; and the first law can be expressed as
__________________________________________.
Name______________________________________________________Date_________________Period___
Colliding Carts- Conservation of Momentum on the Air Track
7. Vector Diagram
a.
b.
c.
d.
Which has the greatest velocity change? _____________________
Which has the greatest acceleration? _____________________
Which has the greatest momentum change? _____________________
Which has the greatest impulse? _____________________
8. Velocity-Time Graph
a.
b.
c.
d.
Which has the greatest velocity change? _____________________
Which has the greatest acceleration? _____________________
Which has the greatest momentum change? _____________________
Which has the greatest impulse? _____________________
The Law of Momentum Conservation
http://www.physicsclassroom.com/Class/momentum/u4l2b.cfm
9. The Law of Momentum Conservation is
______________________________.
10. Write it in equation form.
__________________________________________
11. A 120 kg lineman moving west at 2 m/s tackles an 80 kg football
fullback moving east at 8 m/s. After the collision, both players move east at 2 m/s. Draw a vector
diagram in which the before- and after-collision momenta of
each player is represented by a momentum vector. Label the
magnitude of each momentum vector.
12. What is an isolated system?
Name______________________________________________________Date_________________Period___
Colliding Carts- Conservation of Momentum on the Air Track
13. What are two criteria for the presence of a net external force? Do you have these in an isolated
system? Why?
14. Read the descriptions of the three collisions and evaluate whether or not each collision occurs in an
isolated system. If it is not an isolated system, then identify the net external force.
1)
2)
3)
Real-World Applications
http://www.physicsclassroom.com/Class/momentum/U4L1c.cfm
In detail, discuss the topics below and give two examples for each.
a. the affect of collision time
b. the affect of rebounding
Inelastic Collision



http://hyperphysics.phy-astr.gsu.edu/hbase/inecol.html#c1
View: Car "Rear-Ends" Truck - Inelastic
http://www.physicsclassroom.com/mmedia/momentum/creti.cfm
View: Big Fish in Motion Catches Little Fish
http://www.physicsclassroom.com/mmedia/momentum/fca.cfm
View: Little Fish in Motion is Caught by Big Fish
http://www.physicsclassroom.com/mmedia/momentum/fcb.cfm
15. Define an Inelastic Collision.
Name______________________________________________________Date_________________Period___
Colliding Carts- Conservation of Momentum on the Air Track
16. Combine the equations of conservation of momentum and conservation of kinetic energy to derive an
expression for the fraction of energy loss in an inelastic collision. Show all your work!

View: Situation of wearing seatbelts in a car.
http://hyperphysics.phy-astr.gsu.edu/hbase/seatb.html#cc1
17. Discuss how the stopping distance is related to impact force in stretching and non-stretching seatbelts.
Elastic Collisions

View: Car "Rear-Ends" Truck - Elastic
http://www.physicsclassroom.com/mmedia/momentum/crete.cfm
18. Define an Elastic Collision.
19. Discuss the how the concept of elastic collisions applies to Newton's cradle (swinging balls).
Name______________________________________________________Date_________________Period___
Colliding Carts- Conservation of Momentum on the Air Track
The Coefficient of Restitution ( http://www.racquetresearch.com/coeffici.htm ) is defined in this webpage for
the collision between a ball and a racquet.
1. How is the elasticity related to the kinetic energy?
2. What happens to the kinetic energy in an inelastic collision?
3. What are the values of the coefficient of restitution for the two types of collisions?
Part II. AIR TRACK SIMULATION
INTRODUCTION - The air track is a tool to study one-dimensional motion with friction virtually
eliminated.
The configuration consists of the track itself, air blower, carts and a collection of accessory pieces. The
accessories include rubber band bumpers, wax/pin bumpers, "sails" and other pieces that are easily attached to
the carts.
Go to: AIR TRACK ( http://www.physicslessons.com/exp5b.htm )
Name______________________________________________________Date_________________Period___
Colliding Carts- Conservation of Momentum on the Air Track
PHYSICS I - MOMENTUM LAB
NAME: ________________________
OBJECTIVE - To investigate elastic and inelastic collisions.
Visit http://www.physicslessons.com/exp5b.htm . This simulation models a basic air track with two blocks.
PROCEDURE:
1. Drag the RED Block to the ‘0’ mark on the ruler and drag the GREEN Block to the ‘3’ mark for all
experiments.
2. Click GO to start Simulations
3. STOP the simulation after the blocks reach the end of ruler.
4. Read FINAL VELOCITIES by clicking on the GREEN TAB of the Momentum
Values
5. Set e at ‘1’ for ELASTIC COLLISIONS
6. Set e at ‘0’ for INELASTIC COLLISIONS
Part A. ELASTIC COLLISIONS: QUALITATIVE ANALYSIS
1. After setting the values, click on GO and observe what happens AFTER the collision.
2. Next, answer the questions indicating your observations regarding the velocities (how fast, how slow)
and direction of each mass.
(a) Elastic Collision Case I. m1 = m2

Set the values as:
m1 = 2 kg m2 = 2 kg
v1 = 5 m/s v2 = 0 m/s
1. What happens to Mass 1 (RED)?
2. What happens to Mass 2 (GREEN)?
(b) Elastic Collision Case II. m1 > m2

Set the values as:
m1 = 2 kg m2 = 1 kg
v1 = 5 m/s v2 = 0 m/s
3. What happens to Mass 1 (RED)?
4. What happens to Mass 2 (GREEN)?
Name______________________________________________________Date_________________Period___
Colliding Carts- Conservation of Momentum on the Air Track
(c) Elastic Collision Case III. m1 < m2

Set the values as:
m1 = 1 kg m2 = 2 kg
v1 = 5 m/s v2 = 0 m/s
5. What happens to Mass 1 (RED)?
6. What happens to Mass 2 (GREEN)?
Part B. COLLISIONS: QUANTITATIVE ANALYSIS FOR EACH CASE:
1. Find the values for the FINAL VELOCITIES (v1' and v2') of each block (reading from the Green Tab) and
record the values on the tables.
2. Perform your OWN calculations for MOMENTUM and KINETIC ENERGY showing all your work:
equations and answers.
(a) ELASTIC COLLISION I. (Set e at 1) Show your work!
RED BLOCK
m1 = 3 kg
v1 = 5 m/s
Initial momentum =
Initial KE =
v1' =
Final momentum =
Final KE =
GREEN BLOCK
m2 = 2 kg
v2 = 0 m/s
Initial momentum =
Initial KE =
v2' =
Final momentum =
Final KE
Was momentum conserved? _____________ Was KE conserved? _________________
(b) ELASTIC COLLISION II. (Set e at 1) Show your work!
RED BLOCK
m1 = 3 kg
v1 = 5 m/s
Initial momentum =
Initial KE =
v1' =
Final momentum =
Final KE =
GREEN BLOCK
m2 = 2 kg
v2 = - 4 m/s
Initial momentum =
Initial KE =
v2' =
Final momentum =
Final KE
Name______________________________________________________Date_________________Period___
Colliding Carts- Conservation of Momentum on the Air Track
Was momentum conserved? _____________ Was KE conserved? _________________
(c) INELASTIC COLLISION I. (Set e at 0) Show your work!
RED BLOCK
m1 = 3 kg
v1 = 5 m/s
Initial momentum =
Initial KE =
v1' =
Final momentum =
Final KE =
GREEN BLOCK
m2 = 2 kg
v2 = 0 m/s
Initial momentum =
Initial KE =
v2' =
Final momentum =
Final KE
Was momentum conserved? _____________ Was KE conserved? _________________
If not, find the loss of KE: __________________________________________________
(d) INELASTIC COLLISION II. (Set e at 0) Show your work!
RED BLOCK
m1 = 3 kg
v1 = 5 m/s
Initial momentum =
Initial KE =
v1' =
Final momentum =
Final KE =
GREEN BLOCK
m2 = 2 kg
v2 = - 4 m/s
Initial momentum =
Initial KE =
v2' =
Final momentum =
Final KE
Was momentum conserved? _____________ Was KE conserved? _________________
If not, find the loss of KE: __________________________________________________
CONCLUSION - Describe the main ideas learned in this activity regarding elastic and inelastic collisions. 5
sentence minimum.