
Before posting anything, please review the Physics Forums Global Guidelines.
Again, for some odd reason, people...

Apr2211 05:26 AM
ZapperZ

1 
47,822 
Is it possible to show that the maximum efficiency for a heat engine is given by
\eta = 1  \frac{T_c}{T_h}
where...

Mar2411 05:47 AM
netheril96

4 
13,593 
http://img835.imageshack.us/i/anmol.png/
the graph is as per the link
but my question is that at a particular...

Mar2411 02:22 AM
Sourabh N

1 
1,911 
What is the longest focal length practical for a lens and/or shaped mirror?
I ask because it would be good if we...

Mar2311 11:06 PM
Drakkith

1 
603 
Pardon me if this is the wrong section for this question, but "energy" seemed like a topic that could fit in almost...

Mar2311 09:01 PM
netheril96

9 
4,019 
hi,
How can I show that the chemical potential of an ideal gas µ(T,V ) can be given by:
\mu(T , V , N...

Mar2311 08:27 PM
Curl

4 
3,528 
I am designing an eddy current brake system for use in roller coaster design.
I have the flux density required to...

Mar2311 04:21 PM
os220

2 
1,905 
Dear Friends & Colleagues,
I would like to propose the following Question, Is there a way to technically Measure...

Mar2311 11:39 AM
cleanenergy

2 
2,472 
Dear Colleagues,
I would like to submit to your court the article in which we attempt a physical analysis of living...

Mar2311 09:23 AM
Vladimir Matveev

2 
956 
I have two physics books that state that
U(r) = GMm/r
What I don't understand,is how can potential energy be...

Mar2211 10:39 PM
rcgldr

7 
1,701 
I have to create an object that will accelerate down a ramp and travel for three meters. Once i solve the angle of the...

Mar2211 10:16 PM
ronshore

0 
860 
Hi, I'd like to know what makes a magnifying glass better at starting a fires by focusing the sun light. Is it the...

Mar2211 08:45 PM
Atrika

10 
6,068 
Hello all,
Just wondering if someone can give me a brief explanation of Wood's anomaly with regards to optics.
...

Mar2211 07:16 PM
astrosona

2 
13,564 
Lets say we have a fixed voltage output on a generator... As we load it down (require more current to flow out of...

Mar2211 06:18 PM
Curl

5 
1,085 
In my book, it says that gravity can be thought of as a force in the form of this vector:
F= (GMm)/(x2+y2+z2)*u
...

Mar2211 05:44 PM
HallsofIvy

2 
2,453 
a) If heat flows through a stack of several different layers, what quantity is
the same for each layer? What...

Mar2211 02:24 PM
tytydinky

0 
1,348 
what is the difference between eddy current and induced current? and how could eddy current cause energy loss? does...

Mar2211 12:41 PM
brainyman89

32 
4,637 
We did an experiment using the physical pendulum to measure gravitational acceleration g. A graph is shown in this...

Mar2211 10:27 AM
netheril96

2 
1,497 
Well the question is in the title. Does Malus' Law (http://en.wikipedia.org/wiki/Malus%27s_law ) follow automatically...

Mar2211 09:41 AM
A. Neumaier

3 
7,643 
Often times I read in these forums that the sped of light is C in a vacuum, but is slower in nonvacuum environments....

Mar2211 09:37 AM
A. Neumaier

5 
2,016 
What is the cause of Gravitation?

Mar2211 07:33 AM
jtbell

3 
541 
I'm seeking some clarification on a topic found in Jackson 'Classical Electrodynamics' Chapter 5. This deals with the...

Mar2211 05:38 AM
netheril96

8 
17,143 
just got a bit confused : because acceleration is a vector , so can we define acceleration for speed , that is , if we...

Mar2111 10:05 PM
phymatter

2 
742 
So I'm creating a game. I have a physics engine in the game. There's a use case that I've come up with that I don't...

Mar2111 07:14 PM
DrSammyD

3 
792 
What experiments have been done to prove that the speed of light is constant among all frames of reference?...

Mar2111 06:28 PM
nhmllr

2 
1,162 
Hi,
I was wondering about an issue that we just started in my physics class: we learned that center of mass (CM)...

Mar2111 05:41 PM
K^2

6 
2,861 
Hey rocket folks 
In light of those artists that deal with massive art, like covering an outdooors area with...

Mar2111 12:38 PM
DaveC426913

12 
2,226 
I am having a hard time figuring out the signs for some of these formulas:
First of all, U=Potential Energy...

Mar2111 06:35 AM
tinytim

5 
4,621 
We were working on some Lagrangian and trying to solve it using an ansatz. Due to some problems in the results we got,...

Mar2111 04:45 AM
Bill_K

1 
1,015 
I have a question concerning the electric field of a rotating linear dielectric disk (with angular velocity w) and a...

Mar2011 11:55 PM
phys_1

0 
1,331 
Hi,
I want to solve the forced wave equation
u_{tt}c^2u_{xx} = f''(x)g(t)
(primes denote derivatives wrt...

Mar2011 11:23 PM
nickthequick

3 
1,669 
Hi,
I'm struggling to understand the different friction forces acting on a car. What is rolling friction and what...

Mar2011 09:09 PM
jack action

2 
1,124 
need a hydraulic pump (gpm) ? to drive a hydraulic motor (torque)?  that has to replace a 16 horsepower gas...

Mar2011 08:58 PM
jack action

1 
1,493 
G'day,
Just wondering if someone can explain to me how when an object is moved to a higher point above the earth,...

Mar2011 12:35 PM
rcgldr

10 
2,899 
Ok, I'm studying electric fields this semester, covering Gaussian Law, capacitance, dielectric circuits and dc...

Mar2011 10:55 AM
Ambidext

0 
685 
Here we have got a very long rod (100 million km length or so) built/placed on the lunar surface (near equator) and...

Mar2011 08:24 AM
Vanadium 50

12 
1,352 
how to prove that
(a)(dU/dV)T=0
(b)(dH/dP)T=0
for an ideal gas.

Mar2011 08:18 AM
Vanadium 50

1 
672 
I wanto show that:
\partial_{\mu} T^{\mu \nu}=0 for
T^{\mu\nu} = F^{\mu \rho}\eta_{\rho\sigma}F^{\sigma...

Mar2011 03:44 AM
MathematicalPhysicist

7 
1,371 
Can an object be increasing in speed as its acceleration decreases? if so, give an example; if not explain why.

Mar2011 03:07 AM
abrowaqas

3 
790 
Can anyone tell me what G force would be received when going from 30mph to 0mph in 0feet. This is from involvment in a...

Mar1911 07:43 PM
Lsos

3 
897 
Hi, in class we were talking about lenses and how there is a certain focal length where all images 'far enough' away...

Mar1911 03:53 PM
Andy Resnick

1 
1,001 