Direction Definition and 999 Threads

I read that ##d/dx## is the direction that x increases (paraphrased from Griffiths e-mag). Why is this? I can't find any information online when I search this up. Original text:

Homework Statement: TE and TM polarization parralel question Relevant Equations: its a photo Hello, In the photo on the left bellow E-field is not parralel not to X nor to Z direction. to what exactly is it parralel? Thanks.

Why are the crystallographic direction indices u,v, and w? And as an add on, why are the miller indices h,k, and l? Why did we pick these letters for each? I’m having a tough time remembering which letters to use and some context might help.

I greet everyone I am faced with such a question First 100m to the right, then 300m down, then 150 left diagonally, even I don't think this is exactly right, I think there will be 150x sin30 or cos30, but I'm not sure, I need to do 200xcos60 afterwards, but I couldn't settle the question. can...

I am watching a youtube video and the guy is finding the area of triangles in the coordinate planes as shown in the image still below. So the triangle ABC has area a and normal n with direction cosines {L,M,N}. He then says it is obvious from geometry that the area of triangle OAC is given as...

Tension force = 10lb[W] where do i put tension arrow in the full body diagram

Hi, PF, this thread is meant to be an introduction to the principles of ##DC## and ##AC##, but I'm very much insecure about the rigurosity of my point of view, so I prefer to post at the lounge. There it goes: fasten seat belts :smile: The textbook ("Pre-university Physics Principles", by the...

Hi All, Do the left side and right side engines of a plane rotate in the same or opposite directions? Is the angular momentum (gyroscopic effect) of the engine shaft, blades, etc., sufficient to affect the flight path of a plane with large engines? In military fighters, such an effect could be...

So, I'm working on ODE at this point, and unfortunately I don't have the time to learn all of the Mathematica input for at least a few months. But, I was hoping someone could tell me how to graph direction fields of ODEs, either with the Mathematica input or free-form? Looking through the...

In section 10.1 of "A First Course in GR" by Schutz, in the paragraph directly above equation 10.5, Schutz says "we must have that a line ##r## = const., ##\theta## = const., ##\phi## = const. is also orthogonal to the two-spheres. Otherwise there would be a preferred direction in space. This...

TL;DR Summary: Confusion in φ cap direction for Left & Back face The image of the question is shared at this Imgur link - The only issue I'm facing in this particular problem is in calculating the flux through the "Left" & "Back" faces of this quarter cylinder. More specifically the issue is...

Going through this ( Revision) A salways your insights are quite helpful. I would like to go through all these questions; i will start with (5), ##\left( \dfrac {x} {y} \right)## = ##\left( \dfrac {10 \cos 40^0} {10 \sin 40^0} \right)## + ##\left( \dfrac {4 \cos 150^0} {4\sin 150^0}...

E1= 9.0 x 10^9 * 10 x 10^-9 / (0.045)^2 = 45000. x cos(153.43)= E2= 9.0 x 10^9 * 10 x 10^-9 / (0.02)^2= 22500 x cos(180)= E3= 9.0 x 10^9 * 5.0 x 10^-9 / (0.04)^2= 28125 x cos(90)= ? Enet= ?

I have seen this in pop-science, is it correct? Does antiparticles move in the oppisite direction of time? Is it possible to prove this experimentaly? Does it have any practical consequenses? We use PET-scaning everyday, is there anything to consider when working with positrones connected with...

Consider a circular Amperian loop oriented counterclockwise that is concentric with the circles in the figure and passes through P. By symmetry, ##\vec{B}## is everywhere tangent to this circular loop and has the same magnitude B everywhere on the circle. By Ampere's law...

How would we define a value for acceleration if only the direction is changing and not the speed?

So i found the magnitude which is (-1)^2 + (-2)^2 = P^2 = Sqrt(5) Then I used the inverse tan function to find the angle (direction) theta = arctan (-2/-1) = 63.8 degrees Im confused with my 63.8 degrees since the angle in the graph looks greater than 63.4 degrees I subtracted 180 by 63.8 and...

So far: I an having trouble in the FBD. I drew one completely opposite to one I found on google . in this image NORmal force is pointed away from the cyclist and centripetal force is pointed away from the centre . mine was the complete opposite am i wrong?

The correct answer is obtained by rearranging Δ x/ Δt = v. However, I assumed there would be some acceleration in the y direction so I tried to use the kinematic equations. To find the time I simply rearranged Δ x/ Δt = v, assigning v=5.2 m/s and Δ x = 650. I assumed there is no acceleration in...

At first I thought that this force vector ## \vec F = 3 \hat x + 2 \hat y ## is a function of ## x ## and ## y ##, which is to say that its magnitude and direction vary with the x and y positions, but this is not so, right? It's just a force with a constant magnitude and direction. And I can...

From the picture, the particle experiences upwards force. But how to determine the direction of motion? I think there are two possibilities: if the particle is positive, it moves from Q to P and if it is negative it moves from P to Q. Thanks

Hi I have come across something confusing in rolling motion. If an object moves with a positive V_cm meaning to the right its angular velocity will be clockwise or negative. The formula is V_cm=wR but for a positive V_cm you get a negative w as it moves clockwise if V_cm is to the right...

This is how I interpreted the problem, a) The net torque about point A is zero. This is because the forces F1 and F2 are equal and opposite, and they act at the same distance from point A. Therefore, they produce torques that cancel each other out.. The force F3 doesn’t does not produce any...

Say I have a magic way to exert lateral forces on a free-rolling ball on a plane, with no slipping. Say I apply a force for a given period from the South, the ball starts rolling to the North and attains a constant speed. Then I suddenly apply the same force for the same period but from the...

I don't know if there are some here familiar with "Veritasium", a YouTube video channel dedicated to science and engineering. It was created and is hosted by Dr. Derek Muller. It has over 8 million subscribers and many of its programs have been watched millions of times. Today I was watching an...

The situation is as follows. We have two disk magnets. One is fixed on the ground, table, or surface and has the north pole facing up. Then we have a metal plate fixed on the vertical axis rod or something similar such that it can't move up or down, but only rotate horizontally with as less...

So the only problem I am having is determining the direction of static friction. I did the same problem but while they were going in a vertical circular motion instead, where the static friction force was in the direction of centripetal force (pointing to the center of the circle). Would it be...

After the switch is closed, current flows clockwise from the battery to resistor R1 and down through the switch. I don't understand the reasoning for the following: the current from the capacitor flows counterclockwise and down through the switch to resistor R2. How do I determine the direction...

For this problem, Is the length vector into or out of the page and how do you tell? EDIT: Why must we use conservation of energy for this problem? I tried solving it like this: ##IdB\sin90 = ma ## ##IdB = ma ## ##v_f = (2aL)^{1/2} ## ##v_f = (\frac {2dIBL} {m})^{1/2} ## Which is incorrect...

In the derivation of the conservation law of the conservation of mass, the flux on one side enters and the flux on the other side leaves the control volume. I presume this is due to the assumption that the volume is infinitesimally small and hence v(x,y,z,t) will not change directions...

3 A+ 2 A = 7 A+ I I = -2A How the current can be in negative direction? If the sign if negative, doesn't it mean that the current will move towards the point P? Also If I am taking the 2A to be positive then Kirchhoff's law isn't satisfied as 5A≠7A

I'm using a stainless steel pan and a fan to cool my coffee down as quickly as possible. Usually, I have the fan blowing down towards the coffee, but this morning I flipped it over to suck the heat out of the coffee and I'm wondering which of the two is the most efficient, especially as, in the...

If a lone hydrogen atom in space emits a photon, is it emitted in a particular direction or in a superposition of all directions?

Here's the full code: This is the code that I'm interested in:window.addEventListener("keydown", e => { inputDir = { x: 0, y: 1 }; moveSound.play(); switch (e.key) { case "ArrowUp": inputDir.x = 0; inputDir.y = -1; break; case "ArrowDown": inputDir.x =...

Hi, the problem statement is above. I have some questions about how to calculate the area and the direction of the magnetic field of this problem. As the magnetic flux, my professor have defined it as Phi= integral(B dS)=(Area)e_x B= (Area_triangle + (L^2/2) *(β + α(t)))*B e_z. How can one know...

A basic example to explain what brings about my question is when considering two objects moving away from each other with an object at rest in the middle. In all 3 objects' frames of reference they are going through their respective time axises at the speed of light. It would appear that time...

According to Chapter 8 of Griffiths' book Introduction to Electrodynamics, the magnetization force that acts on a magnetic dipole is $$F_M=\nabla (m \cdot B)$$, where ##m## is the magnetic moment and ##B## is the magnetic field. For a paramagnetic or diamagnetic particle...

Hi, I have a fairly simple question, but the answer is probably not as simple. I'm not sure to understand why in a guided wave (TE), the electric field is in the y direction. I know ##E_z = 0##, but why ##E_x = 0, B_y = 0##?

I have a disk traveling on the inner blue track (let's say the blue part is the center of the disk). I want to push the disk outside (as the disk is traveling in a circle) to the outer track. The black part is the wall separating the tracks To that end, I've made some calculations, but I have...

For the box I understand it’s just normal and force of gravity as well as tension pulling them, it was declared to have no friction so it just points up down and right. It’ll be accelerating right. The second person again has the normal force, gravity and the tension going to the left as a...

Sorry if I post again about this topic (last time I promise!) but I still have some doubts regarding the concept of flux. This collection of problems I have quite standard but there are so many variations. Here is the circuit in question: Something tells me that I could write a function that...

My assumption says,as A moves to the right,there will be kinetic friction acting on it to the left and equal and opposite friction will act on B to the right,so it should move to the right keeping the center of mass go on moving with velocity mv/(m + M) to the right as there is no net external...

Hello : Trying to find references on drawing direction fields of higher order differential equation by hand as 1st step then by computer , do you know any reference I can read ( PDF , books ,...) , and hope it is not only some short notes Best regards HB

Faraday's law tell's you about the line intergal of the electric field, but you have to know the direction of the induced electric field first in order to properly apply it. How can I find its direction? Is it in the same direction as the induced current?

Hi all. I am stuck with a seemingly silly doubt all of a sudden. The direction of Electric Field is taken from Positive to Negative (because Field Lines originate from a Positive Charge and terminate at Negative Charge). We know that direction of Dipole Moment is from Negative Charge to a...

I recently graduated last year with a BS in Physics. To say that it was rough would be an understatement. I started off my degree very well, getting nearly all A's and A-'s. My performance would decline for various reasons, though mostly due to mental health which spiraled and became a bad...

V^2= u^2 +2gh

I am not very sure how I would be approach this. Obviously it is stated in which direction it's going where we see that mass A goes to the right, but how do I determine this stuff analytically.

Do I determine this from the friction coefficients? Such that because mu_b > mu_a I know that it'll push on B because it has a bigger friction coefficient. such that this has nothing to do with the mass of the blocks? or does it? f.e. can I take it to be in an arbitrary direction and then...