Rotational weight vs. dead weight

  • Context: High School 
  • Thread starter Thread starter johnnyphaze
  • Start date Start date
  • Tags Tags
    Rotational Weight
Click For Summary

Discussion Overview

The discussion revolves around the comparison of a rotating wheel versus a stationary wheel, specifically focusing on the implications for weight and fuel efficiency in vehicles. Participants explore concepts related to mass, moment of inertia, and their effects on performance.

Discussion Character

  • Debate/contested, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions whether a rotating wheel is heavier than a stationary wheel, prompting a discussion on the nature of weight and mass.
  • Another participant challenges the initial question by asking why there would be a perceived difference in weight between the two states.
  • A participant introduces the topic of fuel efficiency, suggesting that larger wheels might affect miles per gallon (mpg), proposing that at a constant rate, larger wheels could actually increase mpg.
  • A different participant asserts that both rotating and stationary wheels have the same mass, indicating that weight does not change with rotation.
  • Another contribution emphasizes that while the weight remains the same, the car must also account for the moment of inertia when propelling the wheels, which could impact gas mileage.
  • One participant notes that a heavier "dead weight" would increase the moment of inertia, potentially lowering gas mileage.

Areas of Agreement / Disagreement

Participants generally agree that the mass of the wheels does not change whether they are rotating or stationary. However, there is disagreement regarding the implications of wheel size and weight on fuel efficiency, with differing views on how these factors interact with moment of inertia.

Contextual Notes

The discussion includes assumptions about the relationship between mass, moment of inertia, and fuel efficiency, which are not fully resolved. The impact of wheel size on mpg remains a point of contention.

johnnyphaze
Messages
2
Reaction score
0
I am not sure if I am in the right section, but here goes my question.

Can anyone explain to me which one would be heavier. A rotating wheel or a wheel that is just sitting there?
 
Physics news on Phys.org
Why would you think there would be a difference?
 
well the main debate is "will bigger wheels cause my mpg to go down?"

my answer was is that at a constant rate it would actually increase.


a buddy of mine puts his 2 cents in and states that rotating mass is a lot heavier than dead weight. i am just trying to make logic of that.
 
The answer to you first question is that both still have the same mass.

To answer your "will bigger wheels cause my mpg to go down?" question, you would have to consider the moment of inertia of the wheel and work done.

~H
 
The weight of a mass is the same whether rotating or not.
 
The car not only needs tp propel the "dead weight" of the wheels, but also must generate an angular velocity and acceleration of the wheels, which is determined by calculating the mass moment of inertia. so a heavier "dead weight" would increase the moment of inertia, lowering gas mileage.
 

Similar threads

  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 22 ·
Replies
22
Views
5K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 26 ·
Replies
26
Views
3K