Comparing two expenditures of work

  • Context: High School 
  • Thread starter Thread starter thetexan
  • Start date Start date
  • Tags Tags
    Work
Click For Summary
SUMMARY

The discussion centers on the comparison of work done by two individuals traveling from Central Park, New York, to the Golden Gate Bridge, San Francisco, one walking and the other skateboarding. It establishes that while both individuals move the same mass over the same distance, the concept of "work done" requires clarification regarding the forces involved, such as gravity and air resistance. The metabolic cost of skateboarding is approximately 2.2 J kg-1 m-1, which is lower than that of walking and higher than cycling. This highlights the importance of specifying the context when discussing work in physics versus physiology.

PREREQUISITES
  • Understanding of basic physics concepts, particularly work and energy.
  • Familiarity with forces such as gravity and air resistance.
  • Knowledge of metabolic costs associated with different modes of transportation.
  • Ability to differentiate between physics and physiological perspectives on energy expenditure.
NEXT STEPS
  • Research the physics of work and energy, focusing on the definitions and calculations involved.
  • Explore studies on metabolic costs of various transportation methods, including the referenced article on longboard skateboarding.
  • Investigate the effects of air resistance on different modes of travel and how it impacts energy expenditure.
  • Examine the differences between mechanical work and physiological energy expenditure in human activities.
USEFUL FOR

This discussion is beneficial for physics students, exercise physiologists, and anyone interested in understanding the energy dynamics of different travel methods.

thetexan
Messages
269
Reaction score
13
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
 
Physics news on Phys.org
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.
 
  • Like
Likes   Reactions: Bystander
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."
 
  • Like
Likes   Reactions: jrmichler

Similar threads

  • · Replies 8 ·
Replies
8
Views
765
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 93 ·
4
Replies
93
Views
6K
  • · Replies 25 ·
Replies
25
Views
2K
  • · Replies 11 ·
Replies
11
Views
1K
  • · Replies 21 ·
Replies
21
Views
7K