Does weight / inertia / momentum change with temperature?

Click For Summary

Discussion Overview

The discussion revolves around the question of whether weight, inertia, and momentum change with temperature, based on an experimental observation involving a copper block. Participants explore various explanations for the observed weight difference at different temperatures, considering both physical principles and experimental conditions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant reports an experiment where a copper block's weight changed by 4-5 mg when heated from -2C to 300C, suggesting that inertia and momentum are affected by heat.
  • Another participant proposes that the observed weight change could be explained by buoyancy effects due to thermal expansion, which displaces more air and results in a lower weight reading, while mass remains unchanged.
  • A different viewpoint suggests that condensation of water vapor on cold objects and evaporation of such condensates when heated could also influence the weight measurements.
  • Concerns are raised about potential experimental errors, such as natural convection currents affecting the scale readings and the impact of temperature on the scale mechanism itself.
  • One participant emphasizes the importance of calculating the expected effects rather than speculating, noting that essential information about the direction of the weight change was not provided by the original poster.

Areas of Agreement / Disagreement

Participants express differing views on the causes of the observed weight change, with no consensus reached on whether the effects are due to buoyancy, evaporation, or experimental errors. The discussion remains unresolved regarding the underlying reasons for the weight variation.

Contextual Notes

Limitations in the discussion include the lack of detailed information about the experimental setup, such as the geometry of the experiment and the specific conditions affecting the scale measurements. There is also uncertainty regarding the direction of the weight change observed by the original poster.

quadcatfly
Messages
3
Reaction score
0
I did a simple experiment. I took a small block of copper (40g) and sensitive scales. First I cooled the block in a freezer (-2C) and checked its weight. Then heated it up to 300C in the oven and checked weight again. The difference in weight is well observed (4 - 5mg). Results are consistent and repeatable. The only conclusion I can make from it (apart from the obvious that many formulas in physics don't work in the real world) is that inertia and momentum also get affected with heat.
 
Science news on Phys.org
Can the effect be explained by buoyancy? Hotter -> thermal expansion -> displaces more air -> weighs less, but mass is unchanged.
 
Also, water vapor in the air tends to condense on cold objects. And heating an object that much probably drives off (evaporates) stuff that's condensed on the surface. Not just water, but also oils from fingerprints, etc.

Was the object heavier when hot or when cold?
 
Dr. Courtney said:
Can the effect be explained by buoyancy? Hotter -> thermal expansion -> displaces more air -> weighs less, but mass is unchanged.
Why speculate about this? Why don't you just calculate the effect and see what you obtain?

I don't know the geometry of the experiment, but there may have been natural convection currents in the air (caused by the hot block) in proximity with the scale that could have affected the measurement. Also, how about just the effect of the higher temperature on the scale mechanism?

I don't think that the mass of the block changed.

Chet
 
Chestermiller said:
Why speculate about this? Why don't you just calculate the effect and see what you obtain?

I've done the calculation before. Students learn more if you encourage them to do it rather than posting the result. The OP also posted the magnitude of their observed effect, but not the direction. There is less motivation to chase down explanations when essential information is absent.
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 1 ·
Replies
1
Views
4K
Replies
24
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 7 ·
Replies
7
Views
3K