(Meteoroid), meteor, meteorite

The Simpsons
Episode 4 (382), Season 18
"Treehouse of Horror XVII: Married to the Blob"

The Simpsons family witnesses a meteor landing in their backyard. Homer subsequently eats an alien lifeform found inside the meteorite, to tragicomedic results.

Previous post:
http://waiferx.blogspot.com/2008/03/astronomy-in-class-activity-meteorite.html

Aftermarket after-accident airbag deployment

The Simpsons
Episode 13 (413), Season 19
"The Debarted"
Screencaps from hulu.com

Well after Hans Moleman's car is hit from behind by Marge Simpson, its airbag deploys to comedic results. (As Hans' car appears to be an AMC Gremlin, would that airbag an aftermarket add-on?)

Related posts:
Physics clicker question: airbag effect
Airbags make babies cry

Converging lens focal point

The Simpsons
Episode 14 (414), Season 19
"Dial 'N' For Nerder"
Screencaps from hulu.com

Nelson Muntz encounters the "ant-burning spot," where nominally parallel rays from the Sun (behind Nelson? shadows?) converge to the far focal point, on a hapless ant (that manages to survive).

Astronomy clicker question: extrasolar planet orbits

Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q7.5

Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:

[0.3 points.] How did "extrasolar" giant planets in small, eccentric orbits form?
(A) They were formed very close to their stars, in eccentric orbits.
(B) They were formed very far from their stars, in circular orbits, but their orbits were disrupted by collisions with other protoplanets, and spiraled inwards.
(C) They were formed very far from their stars, in circular orbits, but they lost angular momentum to the protoplanetary disk, and spiraled inwards.
(D) They were produced by material ejected from a collision between two stars.

Correct answer: not revealed yet (see discussion below).

Student responses
Section 4160
(A) : 0 students
(B) : 20 students
(C) : 4 students
(D) : 1 student

Section 5166
(A) : 11 students
(B) : 8 students
(C) : 7 students
(D) : 6 students

The students in section 4160 chose impacts on protoplanets (response (B)) over the correct response (C) of (gradual) angular momentum redistribution, after a discussion earlier in the same lecture about angular momentum transfer from the young Sun to its nebular disk. This prompted a refresher on this same subject immediately afterwards.

In section 5166, after showing the lack of consensus in their replies, students were asked to discuss their responses with each other before responding again, with a moderate shift towards the correct answer.

Student responses
Section 5166
(A) : 8 students
(B) : 8 students
(C) : 13 students
(D) : 3 students

Correct answer: (C)

Bon mots: rotation

"I cannot believe that the inscrutable universe turns on an axis of suffering; surely the strange beauty of the world must somewhere rest on pure joy!"
--Louise Bogan

"Poetry uses the hub of a torque converter for a jello mold."
--Diane Glancy, as quoted in What Is Found There, Ch. 12, by Adrienne Rich (1993)

"The lazy manage to keep up with the earth’s rotation just as well as the industrious."
--Mason Cooley, City Aphorisms, Fifth Selection (1988)

"Let the wheel spin out,
Till all created things
With shout and answering shout
Cast off rememberings..."
--Philip Larkin, “All Catches Alight”

"Spin and die,
To live again as butterfly."
--Christina Georgina Rossetti, "The Caterpillar (Sing-Song)"

"Let the great world spin for ever down the ringing grooves of change."
--Alfred Tennyson, Locksley Hall (1842)

"Your work is to keep cranking the flywheel that turns the gears that spin the belt in the engine of belief that keeps you and your desk in midair."
--Annie Dillard, The Writing Life (1989)

Physics midterm problem: package transported uphill

Physics 5A Midterm 1, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Chapters 1-5 Review and Synthesis Review Exercise 20

[20 points.] A Physics 5A student is going to drive a 15,000 kg flat-bed truck at constant speed up a hill that makes a certain angle with respect to the horizontal direction. A 40.0 kg package sits in the back of the truck. The coefficient of static friction between the package and the truck is 0.310. What is the maximum angle of the hill that the truck can travel up at constant speed without the package falling off of the back? Neglect air resistance. Show your work and explain your reasoning.

Solution and grading rubric:

• p = 20/20:
  Correct. Draws free-body diagram for _only_ the package with tilted axes, with the weight force broken up into w_x = m*g*cos(theta) and w_y = m*g*sin(theta) components. Newton's first law is applied in _both_ x- and y- directions. For the y-direction, Newton's first law gives N = w_y = m*g*cos(theta), and for the y-direction, Newton's first law gives f_s = w_x, or mu_s*N = m*g*sin(theta). Solving for and substituting in for N allows theta to be solved for, resulting in theta = Arctan(mu_s).
  
• r = 16/20:
  Nearly correct, but includes minor math errors. Typically uses N = m*g, but otherwise has f_s = m*g*sin(theta), but otherwise shows complete systematic FBD -> Newton's laws -> algebra approach.
  
• t = 12/20:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Free-body diagrams, application of Newton's laws, and algebra are problematic, but still demonstrates some application of this systematic approach.
  
• v = 8/20:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Some attempt at a free-body diagram, applying Newton's laws, or algebra.
  
• x = 4/20:
  Implementation of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
p: 7 students
r: 6 students
t: 5 students
v: 19 students
x: 6 students
y: 0 students
z: 0 students

A sample of a "p" response (from student 2012) is shown below:

A sample of a "r" response (from student 7137) is shown below, where N = m*g, but otherwise all else is correct:

Physics midterm question: SUV and Mini Cooper collision forces

Physics 5A Midterm 1, spring semester 2008
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 4.16

[10 points.] An SUV collides with a Mini Cooper convertible (of much smaller mass). No one is hurt in this accident. During the collision, is the force exerted on the Mini by the SUV greater than, equal to, or less than the force exerted on the SUV by the Mini? Explain your reasoning using the properties of forces and of Newton's laws.

Solution and grading rubric:

• p = 10/10:
  Correct. According to Newton's third law, the two contact (normal) forces involving the SUV and the car have the same magnitude (but have opposite directions), regardless of their different masses.
  
• r = 8/10:
  As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. E.g., recognizes that the two forces have the same magnitude, but has garbled application of Newton's third law, or recognizes applicability of Newton's third law, but does not realize that the two forces have the same magnitude.
  
• t = 6/10:
  Nearly correct, but argument has conceptual errors, or is incomplete. May state that the forces have the same magnitude, but due to reasons other Newton's third law.
  
• v = 4/10:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. E.g., does not recognize that the two forces have the same magnitude, but still attempts to apply Newton's laws in some manner.
  
• x = 2/10:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 1/10:
  Irrelevant discussion/effectively blank.
  
• z = 0/10:
  Blank.
  

Grading distribution:
p: 12 students
r: 4 students
t: 7 students
v: 19 students
x: 0 students
y: 0 students
z: 0 students

A sample of a "p" response (from student 6154) is shown below:
A sample of a "t" response (from student 1397) is shown below:

Physics midterm question: distance traveled vs. displacement magnitude

Physics 5A (currently Physics 205A) Midterm 1, spring semester 2008
Cuesta College, San Luis Obispo, CA

Could the distance traveled and the magnitude of displacement be different when describing the same motion of an object? Explain your reasoning using an example and discussion of the properties of position, distance traveled, and displacement.

Solution and grading rubric:

• p:
  Correct. Draws a diagram and/or makes a convincing argument that demonstrates that the distance traveled is the "actual winding path" taken from a start position to a finish position, while the magnitude of displacement is the "straight line distance" from start to finish, and can be quite different if an object makes a non-linear trajectory.
  
• r:
  As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. May have some ambiguity concerning displacement or magnitude of displacement, but otherwise makes correct distinction between distance traveled and displacement (magnitude) using an example.
  
• t:
  Nearly correct, but argument has conceptual errors, or is incomplete. Argument mainly based on difference between a scalar and a vector property, i.e., comparison of distance traveled and displacement (as opposed to displacement magnitude).
  
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May involve velocities, forces, and/or net forces.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
p: 29 students
r: 5 students
t: 4 students
v: 3 students
x: 0 students
y: 0 students
z: 0 students

A sample of a "p" response (from student 7667) is shown below, using an example of commuting to/from Cuesta College between parking and re-parking a car:
Another "p" response (from student 7137) is shown below, with an illustrated example:

Astronomy midterm question: cosmic ray exposure

Astronomy 10 Midterm 2, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal M2.3
[15 points.] Discuss the evidence that supports the theory that most of the meteorites found on the surface of the Earth are recent fragments of asteroids.

Solution and grading rubric:

• p = 15/15:
  Correct. Exposure to the high energy particles of cosmic rays on the
  exposed surfaces of asteroids induce radioactive decays. The degree of cosmic ray induced decay products corresponds to amount of time spent exposed to outer space. Since meteorites do not have much of this "space tan," they could not have been exposed to outer space for very long, and thus could only have recently fragmented off from deep within larger asteroids.
  
• r = 12/15:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 9/15:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. May confuse the decay products due to cosmic ray exposure with those that determine the solidification age of a material.
  
• v = 6/15:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Typically argues that a meteorite found on the Earth (which is continuously renewed/resurfaced) must haven been deposited there recently, while not accounting for the possibility that the meteoroid may have broken off of its parent asteroid a long time ago, and spent much of its time until now drifiting through space.
  
• x = 3/15:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 1.5/15:
  Irrelevant discussion/effectively blank.
  
• z = 0/15:
  Blank.
  

Grading distributions:
Section 5166
p: 13 students
r: 4 students
t: 6 students
v: 17 students
x: 23 students
y: 0 students
z: 1 student

A sample "p" response (from student 1337):

A sample "p" response (from student 6258) appealing to "The Space Tan Effect":

A sample "x" response (from student 1426), with credit given for effort rather than merit:

Previous post: Astronomy in-class activity: meteorite types and origins

Astronomy midterm question: showerhead effect

Astronomy 10 Midterm 2, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal M2.1

[15 points.] Explain why the meteors in a given shower would appear to be diverging from a fixed point in the sky, as seen from San Luis Obispo, CA.

Solution and grading rubric:

• p = 15/15:
  Correct. Describes and explains the "showerhead effect," where the parallel paths of comet debris particles appear to diverge away from a fixed point in the sky as the Earth passes through the debris.
  
• r = 12/15:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Typically describes, but does not fully explain the showerhead effect.
  
• t = 9/15:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Solidification age is reset, but due to loss/gain/renewal of unstable isotopes.
  
• v = 6/15:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May discuss cause of meteor showers (when the Earth passes through the dust trail left by a comet), but not
  why they would appear to diverge from a fixed point in the sky.
  
• x = 3/15:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 1.5/15:
  Irrelevant discussion/effectively blank.
  
• z = 0/15:
  Blank.
  

Grading distributions:
Section 4160
p: 21 students
r: 6 students
t: 4 students
v: 6 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 6421) appealing to "The Showerhead Effect":

A sample "p" response (from student 7045) appealing instead to "The Railroad Track Effect":
Previous post: The Showerhead Effect