Estimate Maximum Momentum You've Had: Physics Problem 10-1

  • Thread starter Jimmy Snyder
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In summary: If you were told that everything in the universe had expanded to twice its former size while you slept last night, how would you check to see if it was true? What if all clocks suddenly ran at half speed? What if the mass of everything doubled? What if all those things happened simultaneously?In summary, if something in the universe changed size (length or volume) then you could check to see if it was true by measuring things like clocks that run at different speeds or the mass of things.
  • #1
Jimmy Snyder
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I though you might like a light break to solve a problem probably more interesting than the author intended. This is from Physics, Classical and Modern, by Gettys, Keller, and Skove, 1989 (first?) edition. Question 10-1, page 220.

Estimate the maximum magnitude of momentum you have ever had. In what reference frame?

This is a text for a 2 or 3 semester physics survey course, so the typical reader may be unaware of some reference frames available for answering the question.
 
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  • #2
Meh. Unless you want to be unreasonably nitpicky (e.g., a blowhard) it's abundantly clear that the author means the only frame of reference which matters to 99.999% of people, which is relative to the Earth's surface.
 
  • #3
jimmysnyder said:
Estimate the maximum magnitude of momentum you have ever had. In what reference frame?
If I'm allowed to interpret "maximum" as "supremum", then my answers to the two questions are "[itex]\infty[/itex]" and "none":smile:. These are exact solutions, not estimates.

If I'm not allowed to do that then there is no exact solution.
 
  • #4
negitron said:
Meh. Unless you want to be unreasonably nitpicky (e.g., a blowhard) it's abundantly clear that the author means the only frame of reference which matters to 99.999% of people, which is relative to the Earth's surface.
So, how many points would you take off for those students with more imagination and sense of humor than the book's authors?
A. Einstein said:
The results of Mercury's perihelion movement fills me with great satisfaction. How helpful to us is astronomy's pedantic accuracy, which I used to secretly ricidule.
 
  • #5
Did the words "In what reference frame?" appear in the textbook question, or were they added by jimmysnyder? If they appeared in the question, I think that was an intentional clue to get students to think of alternatives. I very much doubt the authors intended my response in post #3, but they may well have been inviting students to consider a centre-of-earth frame or a sun-centred frame (for example).
 
  • #6
DrGreg said:
Did the words "In what reference frame?" appear in the textbook question, or were they added by jimmysnyder? If they appeared in the question, I think that was an intentional clue to get students to think of alternatives. I very much doubt the authors intended my response in post #3, but they may well have been inviting students to consider a centre-of-earth frame or a sun-centred frame (for example).
In the book. Here's another, from the first chapter on units of measurement. Question 1-4, page 10.

If you were told that everything in the universe had expanded to twice its former size while you slept last night, how would you check to see if it was true? What if all clocks suddenly ran at half speed? What if the mass of everything doubled? What if all those things happened simultaneously?

"Size" is not defined in the book, so it is unclear whether the authors mean length or volume, but volume makes more sense. Also unclear is whether students are allowed to apply what they know about the stability of the atom after having read about m, s, and kg.
 
Last edited:

What is momentum?

Momentum is a measure of an object's motion, calculated by multiplying its mass by its velocity.

How do you calculate maximum momentum?

To calculate maximum momentum, you need to know the mass and velocity of the object. Then, use the formula p = mv, where p is momentum, m is mass, and v is velocity.

What is the unit of momentum?

The unit of momentum is kilogram meters per second (kg·m/s).

Can momentum be negative?

Yes, momentum can be negative. This means the object is moving in the opposite direction of its positive momentum.

How is momentum conserved in a closed system?

In a closed system, the total momentum of all objects before and after a collision or interaction remains the same. This is known as the law of conservation of momentum.

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