How much energy is lost due to friction?

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Homework Help Overview

The discussion revolves around a physics problem involving a sled being dragged by dogs over a horizontal surface, focusing on the work done against friction and the energy lost due to that friction. The subject area includes concepts of work, energy, and friction in mechanics.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between work done by the dogs and energy lost to friction, questioning how to calculate the energy lost. There is discussion about kinetic energy and whether it changes when the sled moves at constant speed.

Discussion Status

Participants have engaged in a back-and-forth regarding the concepts of energy transfer, particularly how work done translates into energy lost through friction. Some guidance has been offered about the nature of energy loss, but no consensus on a specific formula or method for calculating the energy lost has emerged.

Contextual Notes

There is mention of confusion regarding the concepts due to missed class instruction, and participants are attempting to clarify their understanding of energy transformations in the context of the problem.

GiantSheeps
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Homework Statement


A team of dogs drags a 114 kg sled 1.92 km over a horizontal surface at a constant speed. The coefficient of friction between the sled and the snow is 0.124. The acceleration of gravity is 9.8 m/s 2 . Find the work done by the dogs.

Answer in units of kJ.

Find the energy lost due to friction. Answer in units of kJ.

Homework Equations


I don't know, I think that might be part of my problem

The Attempt at a Solution


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For the first one, I did 114 x 9.8 x 1.92 x 0.124 to get 265.982976, which was correct

but for the second part, I tried to do 114 x 9.8 x 1.92 to get 2145.024, which would be the energy with no friction, right? Then I subtracted the energy with friction from the energy without friction to get 1879.041, but that was wrong. What am I doing wrong? Wouldn't it make sense that you could find energy lost like this? Is there a formula?
 
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GiantSheeps said:
Find the work done by the dogs.

Answer in units of kJ.

Find the energy lost due to friction. Answer in units of kJ.
You calculated the work done by the dogs. Where has that work gone? PE? KE? Anywhere else?
 
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Wouldn't it all have gone to KE?
 
GiantSheeps said:
Wouldn't it all have gone to KE?
Sorry if I'm completely missing your point, I missed the class where they talked about this so I'm a bit lost
 
GiantSheeps said:
Sorry if I'm completely missing your point, I missed the class where they talked about this so I'm a bit lost
How do you assess change in KE?
 
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haruspex said:
How do you assess change in KE?

I know that the kinetic energy formula is 1/2mv^2, so to find change in KE I would just use that formula to get the KE and subtract final KE from initial KE
 
GiantSheeps said:
I know that the kinetic energy formula is 1/2mv^2, so to find change in KE I would just use that formula to get the KE and subtract final KE from initial KE
Right. Is the speed changing?
 
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no, the speed is constant
 
GiantSheeps said:
no, the speed is constant
that wouldn't make the answer 0, would it?
 
  • #10
GiantSheeps said:
that wouldn't make the answer 0, would it?
it isn't, can I have another clue, please?
 
  • #11
What is the change in energy of the sled?
 
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  • #12
Wouldn't it also be 0? Becasue the sled is attached to the dogs
 
  • #13
So if the sled didn't gain any energy, what happened to the energy (from the work done by the dogs) from part one?
 
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  • #14
It became friction energy?
 
  • #15
GiantSheeps said:
It became friction energy?
does that even make sense?
 
  • #16
GiantSheeps said:
It became friction energy?
Right.
Well... more correctly, you should say something like, "it was lost through friction." But you have the right idea.

It wouldn't be called "friction energy", it would be in the form of "thermal energy" (because the snow would be a bit warmer).

GiantSheeps said:
does that even make sense?
Haha, not exactly, but you have the right idea.
 
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  • #17
Nathanael said:
Right.
Well... more correctly, you should say something like, "it was lost through friction." But you have the right idea.

It wouldn't be called "friction energy", it would be in the form of "thermal energy" (because the snow would be a bit warmer).Haha, not exactly, but you have the right idea.
Okay I think I'm starting to get it, all of the energy has to go somewhere, so in this case it all became thermal energy
 
  • #18
YES! Thank you so much!
 
  • #19
Wait, but that still doesn't answer the amount of energy lost! What's the formula?
 
  • #20
you don't need a formula for this one
Sl0nimski said:
Wait, but that still doesn't answer the amount of energy lost! What's the formula?
 
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