Comparing two expenditures of work

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Discussion Overview

The discussion revolves around the comparison of work done by two individuals traveling the same distance from Central Park in New York to the Golden Gate Bridge in San Francisco, one walking and the other using a skateboard. The focus includes the concepts of work in physics versus physiological energy expenditure, as well as the implications of different modes of travel on energy use.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the same amount of work is done in both cases, noting that both individuals are moving the same mass over the same distance but using different methods.
  • Another participant emphasizes the need for clarity in defining "work done," suggesting that it depends on the specific forces involved, such as gravity or air resistance, and points out that if both individuals start and end at rest, the net work done could be zero.
  • A third participant introduces the distinction between physics and physiology, arguing that energy expenditure occurs even when a person is stationary, which complicates the comparison if biological factors are included.
  • A fourth participant references existing research on metabolic costs associated with different modes of travel, indicating that skateboarding has a different energy expenditure compared to walking, but does not resolve the original question.

Areas of Agreement / Disagreement

Participants express differing views on the definition of work and its application in this context, indicating that the discussion remains unresolved with multiple competing perspectives on how to approach the question.

Contextual Notes

Limitations include the ambiguity in defining "work done," the dependence on specific forces considered, and the potential influence of physiological factors on energy expenditure.

Who May Find This Useful

This discussion may be of interest to those exploring concepts of work in physics, energy expenditure in physiology, and comparisons of different modes of transportation in terms of energy use.

thetexan
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Let’s say we have two persons who are going to travel from Central Park in New York to the Golden Gate Bridge in San Francisco. One is going to walk and the other is going to use his skate board. And let’s say they weigh the same and take the exact same route.

the question is this...is the same amount of work done (give or take) in both cases? As I understand work, they are both moving the same mass over the same distance albeit using different methods of expenditure of effort.

Another way to ask the question...which would be the better way of travel (considering energy necessary) walk or skate board?

tex
 
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You need to be careful when posing questions of this kind. You say, "the question is this...is the same amount of work done (give or take) in both cases?" "Work done" is too vague. You need to specify the force doing the work. For example, if the persons are initially and finally at rest, the work done by the net force will be zero. If you want the work done by gravity, it will be ##W_g=-mg\Delta h## where ##\Delta h## is the vertical displacement of the persons. If you want the work done by air resistance, ##\dots~## it's complicated.
 
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There is also a difference between physics and physiology. In physiology, a person uses energy (work) even when standing still.

So if you phrased your question using only machines, not biology, it would be clearer that you are asking about physics.
 
It's not an original question. Did you try searching the web with google or the like?

https://pubmed.ncbi.nlm.nih.gov/25085605/
"Self-selected speeds and metabolic cost of longboard skateboarding"
Eur J Appl Physiol, 2014 Nov

"...The gross metabolic cost was ~2.2 J kg(-1) m(-1) at the typical speed, greater than that reported for cycling and ~50% smaller than that of walking."
 
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