# Recent content by wreckemtech

1. ### How can one calculate entropy? What is entropy?

Entropy is a measure of randomness within a system. Another useful way to look at it is "energy no longer available to do work". I'll admit I still have kind of a loose handle on it myself. Entropy is positive or zero for any process. So it's not conserved as other forms of energy are, but...
2. ### Isothermal Process Question

Unless those assumptions are made, there is no way to do basic analysis for ideal systems. And doing in-depth analysis of thermodynamic systems would require higher levels of proficiency in both mathematics and physics than someone taking an introductory thermo class would be expected to have...
3. ### Liquid helium and curved piston

The force from the curved object being moved into will be distributed evenly over all surfaces inside the piston as pressure. Also, the curved object itself is likely to develop an area of higher pressure in front of it as it is moved into the cylinder. That's what happens in real pistons...
4. ### Battery and wire

Sorry to jump in here and muddy things up again, but there will be a magnetic field with flux lines that wrap around the wire axially as soon as the electrons start to move in a certain direction. (Think about right-hand-rule in regards to moving charges and magnetic fields.) So perhaps that...
5. ### Rod at fixed pivot

Yes. The mass moving in an arc really doesn't affect the net KE being generated as a result of it changing elevation. And I'm assuming that the head of the striking implement will be more-or-less perpendicular to the surface of the object it's striking. This means all the velocity will be...
6. ### Rod at fixed pivot

The final kinetic energy, mass times mv^2 will be equal to the vertical distance fallen times gravity times mass, mgh. Set the two equal to each other, and mass cancels out. So you can solve for final velocity. But your device is complicated by the fact that the rod has mass as well, and will...
7. ### Rod at fixed pivot

dPE=-dKE The potential energy stored as the rig is raised will be converted to kinetic energy on the way down. KE=mV^2. Your issue is going to be a little complicated though. Because the rod also has mass of a known linear density and each differential slice dx will be raised a distance of...
8. ### Battery and wire

Okay. So he's saying that as a result of exposure to the voltage, the wire is developing a field of its' own. I don't disagree with this, per se as an explanation for the bulk movement of electrons. It can be demonstrated mathematically using Gauss' equations that there is an axial EM field...
9. ### The Doppler Effect - Finding Velocity of Source

Question 1: is the truck moving towards or away from the detector? Question 2: what equation did you use and what was the answer you got?
10. ### Cherry Pie Entropy

Sorry. I'm new here.
11. ### Battery and wire

The model I proposed is pretty much the classical way electric currents in conductors are modeled. It's incomplete, but it does explain some things. If conduction were completely due to the charges interacting with a field, then why don't batteries short-circuit more easily? If a field in and...
12. ### Battery and wire

From what I understand, it's electrostatic repulsion. The battery will emit electrons at one terminal, and those electrons will "push" on other electrons in the wire and so on down the length of the wire. The other terminal of the battery will also take in electrons at the other end.As a...
13. ### Cherry Pie Entropy

You know, I somehow completely missed the fact that Q was given in the problem statement. I thought the poster was only given T1 and dS. If Q is known, it should be easy enough to substitute something like Q=C(T2-T1) into the first equation, and then C will cancel.
14. ### Cherry Pie Entropy

Generally, S = Q/T. Kind of simplistic, but that is probably what you're going to use to find the net heat transfer into the cherry pie. Then, you'll need to know the heat capacity of the cherry pie to determine the change in temperature. Does the problem statement give the temperature of the...
15. ### E-field greater at sharp edges?

Where there is a flat surface, the charge distribution is even because the exposed surface area of the object per unit volume of space surrounding it is constant. Where you have a sharp edge, or a pointed protrusion on an object, there is more surface area exposed per unit volume of space...