Relative Work - not sure what it means-

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Homework Help Overview

The problem involves two individuals pushing a block on a frictionless surface, with the block moving from rest to rest in opposite directions. The focus is on the qualitative comparison of work done by each person on the block.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the implications of the block's motion and the relative forces exerted by each person. Questions arise regarding the interpretation of "relative work" and the conditions under which the block stops moving.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the question and the implications of the forces involved. Some guidance is provided regarding the nature of work being relative, but no consensus has been reached.

Contextual Notes

Participants express uncertainty about the meaning of the question, particularly regarding the stopping of the block and the relative contributions of each person's work. There is a recognition of the challenge in calculating absolute values in this context.

yttuncel
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Homework Statement



Two people push in opposite directions on a block that sits atop a frictionless
surface (The soles of their shoes are glued to the frictionless surface). If the
block, originally at rest at point P, moves to the right without rotating and ends
up at rest at point Q, describe qualitatively how much work is done on the
block by person 1 relative to that done by person 2?

https://docs.google.com/viewer?pid=bl&srcid=ADGEESibEj7pzQOnOXVNPdE4L1V9YvbZjDsvpoIYd9X36QE73jfnjn3DCgrDR-bbW3An133sPXBv0FACZ65q9TpkFy0t6LlDRzoc3OuWYQmxt4BP_ek_7CKff7heIXLJOepSzUmLmkaW&q=cache%3Apu-zuL8y6zkJ%3Aocw.mit.edu%2Fcourses%2Fphysics%2F8-01sc-physics-i-classical-mechanics-fall-2010%2Fwork-and-energy%2FMIT8_01SC_problems11.pdf%20how%20much%20work%20is%20done%20on%20the%20block%20by%20person%201%20relative%20to%20that%20done%20by%20person%202%3F&docid=c21a27004575c8d09fb3d870f827860c&a=bi&pagenumber=1&w=800

Homework Equations



W = F*dx

The Attempt at a Solution



I could not make up my mind with the question, what it asks. I said from the direction of the motion we know F1>F2 and thus W1>W2. And also W1 is positive whereas W2 is negative. But what else should i say? Shall i say total work is W1-W2 or something like that ?
 
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A strange question! I'm wondering why the motion stops. Does person 2 start pushing harder, to overcome F1 and decelerate the block? Maybe it hits his glued-down shoes.
Anyway, the total work is ultimately zero when the kinetic energy disappears. Before that, all is as you said.
 
Can you please express your opinion about the last sentence of the question? What does it imply by saying "by person 1 relative to that by person 2?" I mean it does not ask about total work, but I feel uncomfortable that I think I am not answering properly if I say things only in post 1.
Thanks!
 
Everything you say is "relative", since you have no way to calculate any absolute numbers.
I'm just thinking of some qualifiers, like F1 > F1 at some point because the box moves to the the right. One does some work on the box and on two. Two absorbs all that work eventually, some gradually, the last of it when the box hits his foot and loses its kinetic energy.