Why does current travel at speed of light rather than speed of sound?
Here's how I understand the situation: when an electrical current is running through a wire, the individual electrons are moving very slowly. The reason that a light bulb turns on so quickly after the...
View ArticleObjects of Different Density in Freefall
Hey all, I was hoping to settle a debate once and for all. Suppose you've got two identical objects, in our hypothetical situation they were mini-vans. One of these is empty and the other is filled...
View ArticleHow was a unit of energy first defined?
How was a unit of energy first defined? I know we measure energy in units of Joules as named after James Prescott Joule and a Joule is defined as 1kg*(m/s)^2 But I can't find any information on the...
View Article3D Rotation of a rigid body in Fixed Axes (Not Axes Rotation)
Dear All, I have come across with a seemingly very simple problem but could not solve it by searching on internet and books. May be I am confused. I want to rotate a 3D body around an arbitrary axis...
View ArticleNet acceleration of the Earth
I'm trying to explain to someone why I think the net acceleration of the earth (due to the sun) is non-zero. My reasoning is that the velocity of the earth is constantly changing. As the sun pulls the...
View ArticleErgodicity for physicists
Textbooks on statistical mechanics usually discuss ergodicity only by words, without presenting any quantitative analysis (equations). On the other hand, serious discussions of ergodicity are usually...
View ArticleChanging magnetic field and a point charge, seems unresolvable
Consider a current loop with a switch and an AC source in space, there is a point charge(electron) inside this loop, my question is, Will the point charge feel any force when we close the switch, i.e....
View ArticleWhy batterys internal resistance decreases with temperature?
Hi, Does battery internal resistance obey the general resistance-temperature rule? For metal, resistance usually increases with temperature (see wikipedia). For batteries however, its internal...
View ArticleWhat are degrees of freedom
I'm starting on lagrangian mechanics and is a little puzzled by the use of generalized coordinates. Shortly, what is a degree of freedom? And what I find harder to understand, why is it that a...
View ArticleAir resistance on bodies in free fall
Hi, In a demonstration that was shown in class, two paper cups were dropped from different heights. The first was dropped from two meters and the other was dropped from one meter. Both landed on the...
View ArticleAcceleration and velocity
Hi, Velocity is defined as speed in a given direction and acceleration is the rate at which velocity changes over time. Lets say a car is being driven on a road. If the speed changes, then the car is...
View ArticleDistance covered in free fall
Hi, As I understand, the distance covered by an object in free fall is described as d = [itex]\frac{1}{2}[/itex]gt2 or d = 5t2 on earth. Objects accelerate at 10 m/s2. Using the first equation, if an...
View ArticleBoundary conditions with dielectrics question
Hi all, I'm doing what should be a pretty simple problem, but some theory is giving me trouble. Basically, in this problem I have a conducting sphere, surrounded by a thick insulating layer, and then...
View ArticleElectric field at point inside a parallel plate capacitor
This doubt is nagging in my mind for couple of days,and its makes the rest of the things so dizzy and confusing.Heres what i thought- What is the electric field at a point inside a parallel plate...
View ArticleWind speed calculation from a pressure setting
I have been out of school a long time, so please go easy on me. If the answer is an equation with symbols or letters, could you please help define them for me? I am trying to calculate the windspeed...
View Articlehow do we decide if a trajectory is 1D, 2D or 3D?
Hello Forum, In kinematics we study motion and the trajectories of moving bodies. The trajectory is a line (straight or curved) that joins all the positions occupied by the object in the various...
View ArticleElectrical and magnetic fields are spherical right?
When i think of electromagnetic waves i think of a fast moving sphere of expanding or contracting fields,either magnetic or electrical depending on where its at in its cycle. So i guess im picturing a...
View ArticleElectron boosted by an electric field
I have an electric field, [itex]\vec{E}=E_0 e^{(x_1-ct)^2}\vec{e_2}[/itex] that boosts an electron that initially is at rest at (0,0,0). I have to calculate the motion of the electron (supposing...
View ArticleCalculating the internal energy of a hydrogen tank? How does it compare to...
Calculating the internal energy of gasoline is fairly simple, because it wouldn't vary much with temperature or pressure. For hydrogen, though, it would vary significantly with each. What sort of...
View Articlecharge distribution on a conductor
Recently I've been trying to understand this subject in more detail. I thought I'd post some of what I've learned here in case either (a) it's useful to others, or (b) others can add to what I've found...
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