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1
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3answers
36k views

Thermodynamics - Sign convention

I use the sign convention: Heat absorbed by the system = $q+$ (positive) Heat evolved by the system = $q-$ (negative) Work done on the system = $w +$ (positive) Work done by the system = $w -$ (...
7
votes
2answers
2k views

Do black holes have infinite areas and volumes?

How to calculate the area / volume of a black hole? Is there a corresponding mathematical function such as rotating $1/x$ around the $x$-axis or likewise to find the volume?
0
votes
1answer
127 views

Thermodynamics - internal energy

What would the curve that describes the change of internal energy ($U$) with the volume ($V$) be like if the change in the temperature is negative? My try: For a ideal monoatomic gas, we have $U=(3/...
3
votes
4answers
18k views

What kinds of materials contract the most in cold temperatures?

I know that water expands in the freezer, but I'm curious about which materials contract in response to cold temperatures --- and most importantly, which ones undergo the most drastic changes?
8
votes
2answers
1k views

Do you pay more for gas when the day is warmer?

Found this at the gas station yesteday - got me thinking...
1
vote
3answers
2k views

Why is density an intensive property?

I am still trying to understand what are intensive and extensive properties. Possibly someone can give a pointer to a decent text (preferably on the web), as I am not too happy (to say the least) with ...
0
votes
2answers
595 views

Point masses and infinite densities

Point masses are masses who don't have volume. It is said that they are infinitly dense, but I though division by zero is undefined hence you can't define the density for a point mass because $\rho=m/...
-2
votes
1answer
118 views

Where is error in this method of finding volume of sphere using integration? [closed]

Where is error in this method of finding volume of sphere using integration?