« first day (3725 days earlier)      last day (1189 days later) » 

antimony
antimony
2:25 AM
in a high enough vacuum is it reasonable to return from statistical mechanics to kinematics?
well, i suppose some kind of 'soft' intersection between the two at least
 
 
11 hours later…
ACuriousMind
ACuriousMind
1:16 PM
@antimony what's reasonable depends on what your goal is - there is nothing about X objects that would make them intrinstically "statistical" or "kinematical" compared to X+1 objects, it's just that as the number of objects grows a detailed kinematical account becomes more and more unfeasible
 
 
3 hours later…
Nihar Karve
Nihar Karve
4:12 PM
Snagged a pirated PDF from a certain "Fulvio Frisone", nice
He supplies everything from Weinberg to Polchinski it seems
 
Ankit
Ankit
5:04 PM
@JohnRennie can you help me with this physics.stackexchange.com/questions/607882/…
 
John Rennie
John Rennie
5:24 PM
@Ankit hi :-)
 
Ankit
Ankit
5:41 PM
@JohnRennie hello
 
John Rennie
John Rennie
@Ankit hi :-)
The key to understanding this is that the work and the KE are not two different thinks. What happens is that some other form of energy is turning into KE.
 
Ankit
Ankit
@JohnRennie can you please help me ?
 
John Rennie
John Rennie
For example suppose we have a spring pushing on a block and accelerating it.
We start with potential energy in the spring, and that PE gets converted into the KE of the block. Energy is flowing out of the spring and into the block. OK so far?
 
Ankit
Ankit
@John Rennie Yes
 
John Rennie
John Rennie
The term "work" just means the amount of energy that has flowed out of the spring and into the block. So it isn't the case that we do work and that work causes the KE to change. When we calculate the work using $\int F.dx$ we are actually just tracking the flow of energy.
 
Ankit
Ankit
5:47 PM
@JohnRennie what about the example I used ?
 
John Rennie
John Rennie
@Ankit in your question you talk about a force being applied to the body, but you don't consider where that force is coming from. Some other system must be transferring energy to the body by applying a force to it. Energy is flowing out of that "some other system" and into the body.
 
Ankit
Ankit
@JohnRennie so as the body starts moving when force is applied this means that it gains kinetic energy and this kinetic energy comes from the source ?
 
John Rennie
John Rennie
Yes.
 
BioPhysicist
BioPhysicist
@Ankit IF you are worried about violating the speed of light, the energy transfer and kinetic energy gain technically happen at the same point in space, so we don't need to worry about violating the speed of light limit
 
John Rennie
John Rennie
Energy is always conserved, so the KE that the object gains has to come from the energy of whatever system is applying the force. In my example of a spring that would be the PE of the spring.
The point is that the work and the KE are the same thing.
 
BioPhysicist
BioPhysicist
5:56 PM
The net work and the kinetic energy are the same thing
Or even better
 
John Rennie
John Rennie
When we talk about doing work we actually mean converting some other form of energy into the KE of the body.
 
BioPhysicist
BioPhysicist
The net work and the change in kinetic energy are the same thing :P
 
John Rennie
John Rennie
OK, "net work" :-)
 
Ankit
Ankit
@John Rennie So the body moves and at the same instant gains kinetic energy. Right ? Its position and velocity changes at the same time ?
 
John Rennie
John Rennie
Yes
 
BioPhysicist
BioPhysicist
6:09 PM
@JohnRennie Bob's answer says otherwise physics.stackexchange.com/a/607896/179151
 
M. Çağlar TUFAN
M. Çağlar TUFAN
Hey everybody
I'm studying sinusoidal forced responses of circuits topics on circuit analysis
But I can't understand the topic
Is there anyone can help me about it?
 
Ankit
Ankit
@JohnRennie Bob D's answer is completely different please help physics.stackexchange.com/a/607896/271783
@BioPhysicist can you help me out now ?
 
BioPhysicist
BioPhysicist
I agree with John here
 
Ankit
Ankit
@BioPhysicist so is Bob wrong ?
 
 
2 hours later…
JMac
JMac
8:00 PM
@Ankit I personally don't agree with his conclusion that "work comes first". His answer really doesn't show that either, it just shows that work and change and kinetic energy are related; and then his conclusion doesn't really follow from the rest IMO.
 
 
2 hours later…
schn
schn
9:58 PM
When current flows from the collector to the emitter in an NPN transistor, is there a voltage drop over it? If yes, then the AND gate schematic using transistors (the middle figure) would not make sense , or?
AND gate
The AND gate is a basic digital logic gate that implements logical conjunction - it behaves according to the truth table to the right. A HIGH output (1) results only if all the inputs to the AND gate are HIGH (1). If none or not all inputs to the AND gate are HIGH, LOW output results. The function can be extended to any number of inputs. == Symbols == There are three symbols for AND gates: the American (ANSI or 'military') symbol and the IEC ('European' or 'rectangular') symbol, as well as the deprecated DIN symbol. Additional inputs can be added as needed. For more information see Logic Gate...
 

« first day (3725 days earlier)      last day (1189 days later) »