399 Group PowerPoint

1. Physics 399
Research Presentation
Impulse-Momentum
Theorem
Gavan Kaizawa
Sam Campbell

2. HCPS III Physics standards
Standard 1: Scientific Investigation –
Discover, invent, and investigate using the skills
necessary to engage in the scientific process.
Standard 2: Nature of Science – Understand
that science, technology, and society are
related.
Standard 3: Matter and Energy conservation
Standard 4: Force and motion

3. Presentation Format follows the
Scientific Method used for
Lab Reports
Physical Observation
Research / Literature Review
Hypothesis
Experiment (safety, materials, procedures)
Analysis (Data Table, Graphs, Sample
Calculations, Error Analysis, Percent Error)
Conclusions
Peer Review

4. Physical Observations
Students observe that various colliding
objects will have a different time interval
due to the impact
Students observe that inelastic collisions
stick together causing the time interval to
be infinite
Students observe that elastic collisions do
not stick together but time interval do vary
over a range of elasticity

5. Research & Literature Search
Impulse is the integral of force over time
measured in SI units of N.s
Applying Newton’s 3rd law, every impulse has an
equal and opposite impulse
Deriving Impulse (J) from Newton’s 2nd Law
Fnet = m.a
= (m.∆v)/∆t
Fnet ∆t = (m.∆v)
Impulse (J) = change of momentum (p)

6. Research & Literature Search
(cont’d)
Unbalanced forces always accelerates an
object
In a collision, an object will experience a
force resulting in a change of momentum
The object will either speed up, slow down
or change directions
Impulse, as well as force and change in
velocity, is a vector quantity

7. Research & Literature Search
(cont’d)
When calculating a quantity is a result
from multiplying units measured by the y-
axis and x-axis, you calculate the area
under the graph for the relevant integral

8. Research & Literature Search
Sources
Baker, Martin John (2009), Physics – Impulse: On-line @
http://www.euclideanspace.com/physics/dynamics/collision/impulse.index
Franklin, Bill (2005), Impulse and Momentum: An AAPT / PTRA
Manual, AAPT: College Park, MD.
Science Joy Wagon (2009), Impulse -When Push Comes to Shove:
On-line @
http://regentsprep.org/Regents/physics/phys01/impulse/default.htm
Spark Notes from Barnes & Nobles (2009), SAT Physics – Impulse:
Online @
http://www.sparknotes.com/testprep/books/sat2/physics/chapter9section2
The Physics Classroom-comPADRE (2009), The Impulse-
Momentum Change Theorem: On-line @
http://www.physicsclassroom.com/class/momentum/U4/1b.cfm

9. Hypotheses
If the mass of an object is increased then
the impulse created by the object will
increase because of the greater force
exerted by the object.
If the elasticity of an object is increased
then the impulse created by the object will
increase because of the greater change in
momentum of the object.

10. Impulse-momentum free fall
lab
In a nutshell:
How mass affects impulse. Drop a solid
wooden ball, racquetball, and tennis ball
onto a force plate and record the impulse
created by each.
How elasticity affects impulse. Drop a
frozen (“inelastic”) racquetball and frozen
(“inelastic”) tennis ball on a force plate and
compare to racquetballs and tennis balls at
room temperature.

11. Safety precautions
No horseplay! (Sam!)
Clear area of trip hazards
Potential electrical hazards when
recharging Vernier LabQuest and laptop
computers
Clean up lab work area when finished

12. Materials
Vernier LabQuest data collector
Vernier Logger Pro software
laptop computer
Vernier force plate
Wooden ball, tennis ball, racquetball
Meter stick and hollow tube
Freezer

13. Equipment set up

14. Procedures
Set up free fall apparatus as shown in
previous diagram.
Collect various balls to test the effects of
masses and degree of (in)elasticity.
Connect the force plate to the LabQuest
unit and set data collection parameters: 2
sec record time, 120 samples/s.
Zero force plate.

15. Procedures (cont’d)
Take individual runs for each ball on the
force plate while recording force and time
data through the LabQuest unit.
Download data into a laptop computer and
analyze with Logger-Pro.
Analyze and present data as force, time
interval of impact, and impulse in a data
table and in graph form.

16. Sample Vernier graph:
2 bounces of a racquetball

17. Sample Vernier graph (cont’d)
First racquetball bounce, zoomed

18. Sample Vernier graph (cont’d)
Impact of first racquetball bounce, zoomed
Demonstrates Integrate function to
calculate impulse.

19. Analysis: Sample Calculations
Impulse = FΔt
We can’t just multiply the peak force (highest
force recorded) by the time interval (Δt) because
throughout the impact the force varies through
time.
Realize that the area under the curve is the
impulse on the force plate by the ball.
Vernier units contain a function called
Integrate that calculates the area under the
curve for you.
 Use Integrate to calculate the ball’s impulse.

20. Analysis: Data table
Ball Type ∆t (sec) Force peak (N) Impulse (N*s)
wood ball 0.0216 165.5 2.043
tennis ball 0.0216 73.5 0.9414
"inelastic" tennis ball 0.0242 65.3 0.9231
racquetball 0.022 65.1 0.6613
"inelastic" racquetball 0.0247 59.3 0.6481

21. Analysis: Data graphs
Ball type vs. Impulse
2.5
2
1.5
1
impulse (N*s)
0.5
0
wood ball tennis ball "inelastic" racquetball "inelastic"
tennis ball racquetball
type
Inelastic vs. elastic impulse differences (zoomed in)
0.92
0.87
0.82
0.77 c
0.72
impulse (N*s)
0.67
0.62
tennis ball "inelastic" tennis ball racquetball "inelastic" racquetball
type

22. Error Analysis
The free fall apparatus helped to maintain
a consistent height for each drop
The experimenter dropping the balls may
had a parallax error when aligning each
ball to drop
The free fall apparatus was resting on the
force plate and could have attributed to a
dampening affect on the data

23. Error Analysis
(con’t)
The balls had to be perfectly aligned in the
center of the free fall apparatus. If they
touched the apparatus during the fall,
friction could have affected the results
The assumption that freezing the tennis
ball and racquet ball over a period of time
will cause the balls to become inelastic; or
rather, become more inelastic

24. Percent Error
-the affect of mass on Impulse-
Since there was no standard impulse
available for comparison (no control in the
first experiment), the data presented
shows a correlation of impulse to mass for
ball dropped (see bar graphs!!!)

25. Percent Difference
-comparing the affects of elasticity-
The percent difference comparing the
affects of elasticity to inelasticity for:
Tennis ball
% difference = [(0.9914 - 0.9231) / 0.9914] 100
= 1.943 % difference
Racquet ball
% difference = [(0.6613 - 0.6481) / 0.6613] 100
= 1.996 % difference

26. Conclusions
If a ball’s mass is increased then it will
have a greater impulse on the object it
strikes.
If the elasticity of an object is increased
then the impulse created by the object will
increase.

27. Focusing activity: clocking your
fastball
How can you figure out an object’s speed
just by measuring how hard it hits another
object?
Students throw a racquetball with all their
might against an immoveable force plate,
as a LabQuest unit records force and time
data.

28. Clocking your fastball calculations
Impulse = FΔt = Δ mv.
We want to solve for v into the plate, not Δv, so
we need to use a highly elastic ball so that vfinal ~
vinitial.
Δv = vfinal – vinitial. Therefore if the ball is perfectly
elastic, Δv = 2v. “Bouncing.”
We can get force and Δt readings from the force
plate, and can measure the mass of the ball.
v = (FΔt)/(2m)
Students convert m/s to mph; compare to Roger
Clemens’ fastball.

29. Other student extensions
Using a GoMotion sensor, students can
record data on a ball’s position as it falls.
Along with force plate data, students can
verify the velocity of the ball at impact
using:
3) Kinematic equations: v = vo + gt
4) Impulse-momentum: v = (FΔt)/(2m)
5) Conservation of energy: v = sqrt(2gh)

30. Mahalo!
Questions?
“Damn it, Jim! The GoMotion detector is less than functional!”