Physics quiz question: completely inelastic lab cart collision

Physics 205A Quiz 4, fall semester 2019
Cuesta College, San Luis Obispo, CA

Two lab carts initially move towards the right along a horizontal track, and make a completely inelastic collision. Ignore friction and drag during this brief collision.


After the collision, the 0.200 kg cart has a speed that is __________ the speed of the 0.500 kg cart.
(A) slower than.
(B) equal to.
(C) faster than.
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (B)

In a completely inelastic collision, the two colliding objects stick to each other such that they have the same speed (and direction) afterwards.

Sections 70854, 70855
Exam code: quiz04JuR4
(A) : 7 students
(B) : 40 students
(C) : 5 students
(D) : 0 students

Success level: 77%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.48

Physics quiz archive: energy conservation, momentum conservation

Physics 205A Quiz 4, fall semester 2019
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855
Exam code: quiz04JuR4



Sections 70854, 70855 results

0- 6 :	** [low = 6]
7-12 :	****
13-18 :	*******
19-24 :	********************** [mean = 21.9 +/- 6.1]
25-30 :	***************** [high = 30]

Online reading assignment: collisions

Physics 205A, fall semester 2019
Cuesta College, San Luis Obispo, CA

Students have a bi-weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing a presentation on collisions.


Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.

""Total momentum of an isolated system is the same before and after a collision. An isolated system is which the vector sum of the average external impulses acting on the system is zero."

"There are three ways to identify collisions: elastic, inelastic, and completely inelastic. They are classified according to whether the total kinetic energy changes due to the collision."

"There are three types of collisions: elastic, partially elastic, and completely inelastic. Kinetic energy is only conserved in elastic collisions because there is no permanent deformation of the objects colliding."

"When objects collide and rebound off each other without causing damage the energy is conserved. However, when two objects collide and are crushed or bent, kinetic energy is lost as heat or from deformation."

"An elastic collision is when there is no damage. Partial inelastic means there is crushing or damage but the objects are no longer touching. Finally complete elastic is when there is damage and the objects are still touching."

"In an elastic collision, the two objects rebound off each other, and ideally there is no permanent damage deformation afterwards. Even though there is no cosmetic damage in this collision there was minor structural damage, but this is close to a ideal elastic collision."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.

"I am confused on where the kinetic energy is exactly transferred to, depending on if it's an elastic or inelastic collision."

"How kinetic energy is related to the different types of collisions. I also don't understand momentum conservation."

"I found the principle of conservation of linear momentum to be confusing for me. The textbook it states 'the total linear momentum of an isolated system remains constant. An isolated system is one for which the vector sum of the average external forces acting on the system is zero.' Something about this definition just did not fully click for me and I'm hoping lecture will help me to gain a better understanding."

"I don't understand anything about conservation of momentum. I don't understand how the internal and external forces affect the collision, or when the net force is zero or not. I also don't understand how to tell if the kinetic energy is the same or not before/ after a collision."

"The mathematical analysis of collisions are difficult to interpret correctly."

"I found using the equations confusing especially when deciding when a velocity is negative or positive."

"I'm confused on how to use the momentum and kinetic energy conservation equations."

"Is momentum the same as kinetic energy?"

Explain the difference between a (partially) inelastic collision and a completely inelastic collision.

"In a partially inelastic collision, the two objects collide and rebound off each other but there is permanent damage done afterwards. In a completely inelastic collision, the two objects will collide and stick together."

"With both inelastic collision types, the kinetic energy of the system after the collision is not the same as the kinetic energy of the system before a collision and the objects still separate, but with completely inelastic the objects will stick together."

"Partially inelastic results in damage to the objects but they do not become stuck. Completely inelastic is when the objects become stuck and are physically altered. More damage means more kinetic energy loss."

Explain why drag, friction, and other external forces do not matter during sufficiently "brief" collisions, in order for momentum to be conserved.

"The contact forces during collisions are so large compared to the external forces such as friction and air resistance that we neglect them."

"The drag, friction, and other external forces do not matter during sufficiently 'brief' collisions because those impulses would be almost negligible in at such a short time period."

"They are negligible due to the relatively brief time that collisions take place, so if we look at the left (external impulse) side of the momentum conservation equation we can set it equal to zero, so the objects are exchanging momentum."

"I don't fully understand to be honest."

For the Nissan Altima and Nissan Rogue crash test, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	[0]
(Partially) inelastic.	********************************** [34]
Elastic.	** [2]
(Unsure/lost/guessing/help!)	** [2]

For the Ford Explorer and Ford Taurus crash test, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	** [2]
(Partially) inelastic.	****** [6]
Elastic.	**************************** [28]
(Unsure/lost/guessing/help!)	** [2]

For the train and minivan crash, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	**************************** [28]
(Partially) inelastic.	*** [3]
Elastic.	***** [5]
(Unsure/lost/guessing/help!)	** [2]

For the bullet burrowing through and back out of the baseball, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	***** [5]
(Partially) inelastic.	*************************** [27]
Elastic.	*** [3]
(Unsure/lost/guessing/help!)	*** [3]

For the bullet shot out of this gun, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	*** [3]
(Partially) inelastic.	************ [12]
Elastic.	***************** [17]
(Unsure/lost/guessing/help!)	****** [6]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Which type of collision consists of one object being damaged but the other object was not altered in any way?" (Even if only one object was damaged, then that would make it either a partially inelastic collision (if they separated afterwards) or a completely inelastic collision (if they stuck together afterwards). An elastic collision is only if both objects are undamaged and separated afterwards.)

"Is there such a thing as a partially elastic collision?" (That would be covered under the partially inelastic collision category.)

"Can a collision actually be elastic even with drag air resistance?" (On the smallest scale, gas atoms and molecules bounce off each other elastically with no energy loss.)

"It was harder than I thought to determine which one of those were elastic or inelastic or completely inelastic."

"Will we be looking at car crashes and how it relates to the three types of collisions in lab?" (Yes, specifically the completely inelastic collision type.)

"I'm a little confused when deciding whether or not a collision is completely inelastic or partially inelastic. What happens if one object goes completely through the other?" (As in the bullet goes into the baseball and comes out the other side, there is permanent damage done, so some kinetic energy was lost, such that this makes it a (partially) inelastic collision.)

"I think this is the first thing I have somewhat understood all semester so far."

Physics midterm problem: categorizing a cart collision

Physics 205A Midterm 2, fall semester 2018
Cuesta College, San Luis Obispo, CA

A 0.90 kg cart traveling in the +x direction at 0.45 m/s collides with a 0.15 kg cart that is initially at rest. The carts are not stuck together after the collision. After the collision, the 0.90 kg cart continues traveling in the +x direction at 0.35 m/s. Ignore friction, drag and other external forces during this brief collision. Find (a) the final velocity of the 0.15 kg cart, and (b) classify this collision as elastic, inelastic, or completely inelastic. Show your work and explain your reasoning using properties of collisions, energy (non-)conservation, and momentum conservation.


Solution and grading rubric:

• p:
  Correct. Finds final speed v_f2 = +0.60 m/s of the 0.15 kg cart, using conservation of momentum (as there is negligible drag/friction for this brief collision). It is not known whether the carts are permanently deformed and/or energy was lost to thermal/sound systems, so collision could be either inelastic or elastic (but cannot be completely inelastic because the carts are not stuck together after the collision). Explicitly tests for whether or not translational kinetic energy is conserved, and finds that since it is not conserved, this collision must be inelastic.
  
• r:
  Nearly correct, but includes minor math errors.
  
• t:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Has correct v_f2 from momentum conservation, and at least some attempt at testing for translational kinetic energy conservation.
  
• v:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Application of momentum conservation, but v_f2 is incorrect, with little or no test of kinetic energy conservation.
  
• x:
  Implementation of ideas, but credit given for effort rather than merit.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Sections 70854, 70855
Exam code: midterm02r3iN
p: 28 students
r: 7 students
t: 13 students
v: 4 students
x: 5 students
y: 0 students
z: 0 students

A sample "p" response (from student 1408):

Physics quiz question: partially inelastic lab cart collision

Physics 205A Quiz 4, fall semester 2018
Cuesta College, San Luis Obispo, CA

Two carts initially move towards each other on a horizontal track, and make a partially inelastic collision. Ignore friction and drag during this brief collision.


Based solely on the information given for this collision, the two lab carts:
(A) rebound with no deformation.
(B) rebound after unsticking, with some deformation.
(C) are stuck together with no deformation.
(D) are stuck together and are permanently deformed.

Correct answer (highlight to unhide): (B)

In a partially inelastic collision, some translational kinetic energy is lost to deformation, but the two colliding objects rebound such that they are not stick to each other afterwards.

(Response (A) is for an elastic collision; response (D) is for a completely inelastic collision.)

Sections 70854, 70855
Exam code: quiz04W3rK
(A) : 1 student
(B) : 50 students
(C) : 0 students
(D) : 0 students

Success level: 98%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.07

Physics quiz archive: energy conservation, momentum conservation

Physics 205A Quiz 4, fall semester 2018
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, version 1
Exam code: quiz04W3rK



Sections 70854, 70855 results

0- 6 :	* [low = 3]
7-12 :	********
13-18 :	**************
19-24 :	****************** [mean = 19.6 +/- 6.4]
25-30 :	********** [high = 30]

Online reading assignment: collisions

Physics 205A, fall semester 2018
Cuesta College, San Luis Obispo, CA

Students have a bi-weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing a presentation on collisions.


Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.

"There are three different types of collisions: completely inelastic, partially inelastic, and elastic. And each of these collisions can either conserve or not conserve kinetic energy."

"An inelastic collision is where the kinetic energy is not conserved. A completely inelastic collision is where it sticks together afterward, while partially inelastic collisions deform but don't stick together afterwards."

"The differences between inelastic and elastic collisions and how to identify them. Inelastic collisions (partial or complete) do not conserve kinetic energy, while elastic collisions do."

"An elastic collision is where two objects rebound and there is no permanent damage. Also, only elastic collisions conserve kinetic energy since there is no damage."

"Momentum is conserved for any collision as long as it is brief, the time is so short it becomes zero. Kinetic energy is conserved during elastic conclusions."

"When collisions happen during a very short period of time the left side of the momentum conservation equation can be set to 0. Basically when you are looking at a collision that happens in a short period of time you are just examining the exchange in momentum between the two objects."

"The different types of collisions and the rules for colisions. The conservation laws and the flowchart for them made perfect sense to me."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.

"The flowchart in the presentation was hard to understand. Also, the equation for momentum conservation look intimidating."

"I was confused by the principle of conservation of linear momentum."

"The equation for the conservations kind of confusing. I would just like to see examples worked out in class."

"I had a little trouble understanding the difference between elastic and inelastic collision. Elastic collision is when two objects collide head on and no heat or other form of energy is produced during the collision. Inelastic collision have some thermal and sound energy produced so kinetic energy is not conserved?"

"Categorizing collisions and determining kinetic energy conservation (I did read kinetic energy is only conserved for elastic collisions because none is permanently lost in deformation). Applying conservation law(s) for collisions."

"What I found confusing was why partially inelastic has kinetic energy lost but I think I understand it now."

"When we read the question it is very important to understand what happens after colliding. Sometimes I get confused about this."

"I understood everything in the presentation/textbook...for now anyway."

"I actually understood what this reading assignment was about."

Explain the difference between a (partially) inelastic collision and a completely inelastic collision.

"A partially inelastic collision is where two objects bounce off of each other. A completely inelastic collision is where objects do stick to each other. Permanent damage is present in both cases."

"A partially inelastic collision is when two objects rebound off each other but there is some permanent damage afterwards and a completely inelastic collision is when two objects collide but they stick together."

"A partially inelastic collision has a small rebound with damage and a completely elastic collision has no rebound and the two crashing objects become 'stuck' to each other."

Explain why drag, friction, and other external forces do not matter during sufficiently "brief" collisions, in order for momentum to be conserved.

"The time is so small that the friction is negligent."

"We can neglect their impulses because the brief collision occurs in an instant, so δt would be zero."

"External forces/impulses would be negligible in the relatively brief time that collisions occur."

"Because collisions happen in such a brief time, external forces do not factor."

"These 'brief' collisions happen in a fraction of a second so even though these forces can be quite large their impulses are negligible because of the amount of time they take place in. So momentum is conserved because the objects will only exchange momentum."

For the Nissan Altima and Nissan Rogue crash test, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	* [1]
(Partially) inelastic.	********************************* [33]
Elastic.	** [2]
(Unsure/lost/guessing/help!)	* [1]

For the Ford Explorer and Ford Taurus crash test, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	** [2]
(Partially) inelastic.	***** [5]
Elastic.	**************************** [28]
(Unsure/lost/guessing/help!)	** [2]

For the train and minivan crash, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	******************************* [31]
(Partially) inelastic.	*** [3]
Elastic.	** [2]
(Unsure/lost/guessing/help!)	* [1]

For the bullet burrowing through and back out of the baseball, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	*** [3]
(Partially) inelastic.	*********************** [23]
Elastic.	******* [7]
(Unsure/lost/guessing/help!)	**** [4]

For the bullet shot out of this gun, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	***** [5]
(Partially) inelastic.	************ [12]
Elastic.	*************** [15]
(Unsure/lost/guessing/help!)	***** [5]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"How can you tell if something gets damaged during a collision, such as when firing a gun? Should we just have real-world knowledge or should we know this from examples?" (You'll practice this in class; basically any process that removes or adds kinetic energy counts as "damage.")

What would be the collision if the object went through the other object, for example a bullet going through another object." (That counts as "damage," and since the bullet and object are not stuck together afterwards, then this would be a partially inelastic collision. (If the bullet was embedded in the object, such that they are "stuck together," then this would be a completely inelastic collision.)

"Kinetic energy is all lost when you have completely inelastic collision?" (Well, not all of it is lost, but enough of it is lost such that the objects stick together (rather than rebounding) after the collision, even if they both still have some motion together afterwards.)

Physics midterm problem: American Airlines Flight 1498 bird strike

Physics 205A Midterm 2, fall semester 2017
Cuesta College, San Luis Obispo, CA

"Bird slams into Miami-bound flight on approach to airport"
WPLG Local 10 News
local10.com/travel/bird-slams-into-miami-bound-flight-on-approach-to-airport-1-1

In November 2017, an Airbus 319 collided with a bird that embedded itself into the nose cone of the airplane.[*] Assume that the Airbus 319 had a mass of 62,600 kg and a horizontal speed of 70 m/s while landing[**][***], as it hit the bird (presumably a turkey buzzard[****][*****][******]) of 2.0 kg, flying away from the plane at its maximum speed of 27 m/s. No one was injured on the plane, but the bird was mostly likely instantaneously killed. Ignore friction, drag, and external forces.



Determine (a) the final speed of the plane and bird together after the impact, and (b) demonstrate that the bird experienced a crash severity (Δv = v_f – v₀) with a greater magnitude than the crash severity of the plane.



Show your work and explain your reasoning using properties of collisions, velocities, and momentum conservation.

[*] miamiherald.com/news/local/community/miami-dade/article184658633.html.
[**] wiki.pe/Airbus_A319.
[***] answers.com/Q/What_is_the_landing_speed_of_an_Airbus_A319?#slide=2.
[****] felid.org/activities/page_24.htm.
[*****] wiki.pe/Turkey_vulture#Description.
[******] kern.audubon.org/tvfacts.htm.

Solution and grading rubric:

• p:
  Correct. Determines/discusses:
  1. the final velocity of the airplane (and bird) in this completely inelastic collision from applying momentum conservation; and
  2. the relatively large crash severity magnitude of the bird (essentially 43 m/s), compared to the minuscule crash severity magnitude of the airplane (essentially zero).
• r:
  Nearly correct, but includes minor math errors. Correct final velocity of airplane/bird after collision, but does not find/compare relative crash severity magnitues; or sets up but does not successfully complete momentum conservation for this completely inelastic collision due to math errors, but attempts to use final velocity values to compare relative crash severity magnitudes.
• t:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Typically has at least one final velocity set to zero, and/or does not realize that the final velocities of the airplane and the bird are identical in setting up momentum conservation.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least some systematic attempt at using momentum conservation.
• x:
  Implementation of ideas, but credit given for effort rather than merit. No clear attempt at applying momentum conservation.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Sections 70854, 70855
Exam code: midterm02bu2Z
p: 37 students
r: 7 students
t: 5 students
v: 1 student
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 4632):
Another sample "p" response (from student 5203), with an added "whoops" for emphasis:

Physics quiz question: completely inelastic collision case study

Physics 205A Quiz 4, fall semester 2017
Cuesta College, San Luis Obispo, CA

The following case study was reported on a collision law firm website:

Richard and his wife were [in] the last of a line of cars stopped for a red light. The vehicle behind Richard's didn't stop and rammed his car while going [approximately 10 m/s]. Richard's car was damaged on the rear, and it cost almost $6,000 to repair the damage.

Assume that both cars were stuck together after this accident. Ignore friction, drag, and external forces during this brief collision. Based solely on the (original and additional) information given for this collision, __________ must have been conserved.
(A) translational kinetic energy.
(B) momentum.
(C) (Both of the above choices.)
(D) (Neither of the above choices.)

[*] all-about-car-accidents.com/resources/accidents/car-accidents/examples-rear-end-car-accid.

Correct answer: (B)

Negligible net external force and brief time duration for this collision makes the external impulse on this system zero, such that momentum is conserved. Since both cars are stuck together after the collision, some translational kinetic energy was irreversibly lost in deformation, such that it is not conserved for this completely inelastic collision.

Sections 70854, 70855
Exam code: quiz04w33N
(A) : 6 students
(B) : 31 students
(C) : 4 students
(D) : 7 students

Success level: 65%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.26

Physics quiz archive: energy conservation, momentum conservation

Physics 205A Quiz 4, fall semester 2017
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, version 1
Exam code: quiz04w33N



Sections 70854, 70855 results

0- 6 :
7-12 :	***** [low = 9]
13-18 :	****************
19-24 :	**************** [mean = 20.8 +/- 5.7]
25-30 :	*********** [high = 30]

Online reading assignment: collisions

Physics 205A, fall semester 2017
Cuesta College, San Luis Obispo, CA

Students have a bi-weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing a presentation on collisions.


Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.

A completely elastic collision is where the translational kinetic energy has been completely conserved. A completely inelastic collision has almost all of the kinetic energy transformed into permanent deformation."

"Inelastic collisions can either be partial or completely inelastic. The difference lies between whether or not they both bounce back away from each other. All inelastic collisions cause deformation and therefore lose energy and momentum within the system."

"Elastic collisions cause no physical damage to the objects and kinetic energy is conserved. Inelastic collisions do not conserve kinetic energy and damages at least one of the objects involved."

"If there is no rebound, then its inelastic, if it's partially off, then its partially inelastic and if there was no damage than its elastic."

"The concept of internal and external forces. How internal forces are the forces done by the system that are released upon each other. While external forces are the forces exerted on the objects/system by what is around the system itself."

"The collision type flow chart and the kinetic energy conservation flow chart makes a lot of sense. I would say I understand the difference between each of the collisions and whether kinetic energy is conserved."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.

"The flowchart in the online blog part of the reading was a little confusing at first, but I was able to essentially memorize it after staring at it for long enough."

"The different types of collisions."

"How would you go about figuring out if a collision was going to be elastic or inelastic? Could you also figure out the force that is being exerted by the objects?"

"The flowchart in the online blog part of the reading was a little confusing at first, but I was able to essentially memorize it after staring at it for long enough."

"I'm a little confused about the bullet passing through the baseball."

"The conservation of kinetic energy is a little confusing for this. I can definitely use some help with the formulas and equations."

"What is considered and applied in the situations of external and external forces I found somewhat confusing. As an internal force isn't necessarily something you can track in a sense."

"I would appreciate a brief review of momentum conservation. I think the equation is slightly confusing."

"I didn't find one thing in particular confusing, but I would enjoy some more explanation and review of the information in the presentation. Some example problems to show application would be helpful too."

"I didn't seem to have any problems with this section as the concepts are pretty straightforward. I think I will only really need practice in how to apply it to an example."

"Everything was clear!"

"I like this chapter."

Explain the difference between a (partially) inelastic collision and a completely inelastic collision.

"a partially inelastic collision and a completely inelastic collision differ because a partially inelastic collision does not have the two objects stuck together, but still has permanent deformation."

"A partially inelastic collision is when the objects rebound. While complete inelastic is they stick together."

"A completely elastic collision is one in which the two objects that crash move together as one. A partially inelastic collision is one in which the two objects cause damage, but are separated form each other."

"Partially inelastic collision is when two objects collide they release from one another, but are deformed in some way. While complete inelastic collision is when two object collide together and stick together."

"Whether the objects are stuck together or apart with lasting damage."

"I have no idea."

Explain why drag, friction, and other external forces do not matter during sufficiently "brief" collisions, in order for momentum to be conserved.

"We are limiting our discussion to the initial state before the collision and the final state directly after the collision since it all happens in fractions of a second."

"Since its a brief collision there's such a small amount of time for any of those forces to become impactful."

"Their magnitudes are very small compared to the other forces at play in the collisions."

"I don't know the answer to this."

"Having trouble with this concept."

"I am not sure."

For the Nissan Altima and Nissan Rogue crash test, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	[0]
(Partially) inelastic.	*************************************** [39]
Elastic.	* [1]
(Unsure/lost/guessing/help!)	[0]

For the Ford Explorer and Ford Taurus crash test, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	* [1]
(Partially) inelastic.	****** [6]
Elastic.	********************************* [33]
(Unsure/lost/guessing/help!)	[0]

For the train and minivan crash, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	************************************ [36]
(Partially) inelastic.	** [2]
Elastic.	** [2]
(Unsure/lost/guessing/help!)	[0]

For the bullet burrowing through and back out of the baseball, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	****** [6]
(Partially) inelastic.	************************ [24]
Elastic.	******* [7]
(Unsure/lost/guessing/help!)	*** [3]

For the bullet shot out of this gun, classify the type of collision. (Neglect drag/friction/external forces during this "brief" collision.)

Completely inelastic.	[3]
(Partially) inelastic.	******************** [20]
Elastic.	**************** [16]
(Unsure/lost/guessing/help!)	* [1]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"How many equations are there for these types of problems?" (If momentum is conserved, just one equation.)

"Applications and definitions in normal words would help."

"The flowcharts really help me try to find a baseline of information for each new concept!"

"I think I get this. :) Also loved these short videos!"

"What would you recommend for better preparing for the next midterm?" (I was just about to ask the class about this, for the "Keep-Quit-Start" mid-semester resolution survey.)

"Where can we find the extra-credit surveys?" (Look under Tuesday's homework. Also don't forget that each group "scratcher" quiz in class is also extra-credit.)