Direction Definition and 999 Threads

After much questioning and soul-searching I got my answers of why galaxies rotate, and for that I greatly thank the gurus in the forum (so I'll not forget: conservation of initial angular momentum, non-isotropic material scattering, slowdown of infalling materials and non-isotropic infalling of...

We know that skin depth in a conductor is found using the following expression, (Credits: http://farside.ph.utexas.edu/teaching/315/Waves/node65.html) Basically, as the wave propagates in a conductor, it's electric field strength reduces and reaches 1/e of it's initial value at the skin depth...

Homework Statement We have a yo-yo and the force ##F## which is the tension in the string and this is at the top tangent as shown in the figure attached with this problem. I want to figure out the direction of the friction at the point of contact. Homework Equations Newton's laws of motion...

Homework Statement [/B] Hopefully this is in the correct section I looked around for others but this seemed like the right one. Find the scalar, vector, and parametric equations of the plane that passes through the points P(1,0,4), Q(3,1,-6), and R(-2,3,5). Homework EquationsThe Attempt at a...

We say that buyont force act upwards (in usual cases) and that the normal force exerted by the base of a container (of liquid) on a object is less than its true weight, so a weghing machine will give smaller reading (in terms of value) than expected. But suppose a cube sinks in water. Now water...

So it all starts with the fact that the game Return of the Obra Dinn (I love it, just in case you wonder) won Best Art Direction during The Game Awards 2018. We discussed it here with a friend of mine and turned out we understood the name of the category differently. In Polish direction and...

Homework Statement A vector r has length 21 and direction ratio's 2,-3,6. The direction cosines of r, given that r makes an obtuse angle with x-axis is given by? Homework Equations l/a = m/b =n/c ...(1) (l,m,n are direction cosines, a,b,c are direction ratios l^2 + m^2 + n^2=1...(2) The...

Homework Statement Part a of the image below. When I try to solve this question, I can't get the solution in the answer key. In the answer key the y component of the normal force is NCos(alpha) in the last line. Does the normal force not point perpendicular to the ramp? Homework Equations...

Homework Statement A line makes some angle T with each of x and z axis, and angle U with y-axis so that sin^2(U)=3sin^2(T). Homework Equations 2cos^2(T)+cos^2(U)=1 ...(i) cos^2(x)+sin^2(x)=1 The Attempt at a Solution Using the above two eqns. give us the correct value for cos^2(T) which is 3/5...

Is it a fair prediction to state that in the next several years or so, globally, there will be major investments into gravitational wave research, and many more ‘LIGOs’ being developed? Is it a good idea to venture into that area of physics?

I often get confused that why we have to use the ancient idea for the direction of current flowing.I have come to know a very weak reason for it.It is said that when current was first discovered,it was assumed that the current flows from the positive region to the negative region(using the idea...

We all know that the area of a triangle having consecutive sides as ##\vec { a }## and ##\vec { b }## has the area ##\frac { 1 } { 2 } | \vec { a } \times \vec { b } |## but what is the direction of that area vector? I mean if we consider ##\vec { a } \times \vec { b }## that will be one...

Object with mass ##m## is sliding down a sloped (incline = ##\alpha##) object of mass ##M##. The coefficient of kinetic friction acting between ##m## and ##M## is ##\mu##. There is no friction between object ##M## and the ground. In the drawing above, the red vectors above are the forces acting...

In Torque-Free Precession of a plate, can the direction of the Wobble be either in the spin direction or retrograde to it? For instance if you tossed the plate upward vs downward with the same spin direction. Would the wobble direction and frequency be inverse?

Homework Statement I'm working through an example with motional EMF and I'm having trouble understanding the directions of vectors so that I can apply induction law. The magnetic circuit seems complex because the circuit is used to analyze other situations but the air gap 3, the coil 3 and the...

If all three quarks in a baryon have the same flavor, they all spin the same direction, causing the baryon to have 3/2 spin. In a proton, do both up-quarks spin in the same direction (with the down-quark spinning opposite)? Or can the two up-quarks spin in opposite directions?

Homework Statement The figure below shows a small circular loop of wire in the plane of a long, straight wire that carries a steady current I upward. If the loop is moved from distance x_2 to distance x_1 from the straight wire, what will be the direction of the induced current in the loop and...

Homework Statement A proton moves with a speed ##v = 3 \cdot 10^5 \frac{m}{s}## in the parallel direction to ##i+k##. A magnetic field of ##1T##, in the ##i+j+k## acts over it. Which electric field must we apply in this region so that the Lorentz force over the proton is null? Homework...

To start of, I'm new to physics Forums. My thoughts this evening are directed to a physics question. "How to calculate a direction of a wave". The things i believe i need is three sensors that indicates When the wave passes the equipment. I will measure each specific time and compare them...

I used the following links: C++ software using elliptics integral at: https://tiggerntatie.github.io/emagnet/offaxis/elliptic_c.htm And the calculator here: https://tiggerntatie.github.io/emagnet/offaxis/iloopcalculator.htm I placed some values and obtained Br smaller than Bx, so I do not know...

Homework Statement in the attached file Homework Equations Momemtum = mass - velocity The Attempt at a Solution I solved it E. Since object 2 has the larger mass, the effect is less and will move backwards a little bit.

Homework Statement The question askes about the path of the electron. I need to know if I am doing it correctly whether it was asked for a proton or an electron. Homework Equations F=QV⊥Bsinθ The Attempt at a Solution I answered it C. Because it is an electron, I used my left hand. My thumb...

<Moderator's note: Moved from a homework forum.> 1. Homework Statement Is the gradient perpendicular to all surfaces or just level surfaces? For instance, if I I have a function f(x,y)=z where z is the dependent variable then that is a surface, wouldn't that be a level surface to a function of...

If i have two blocks on top of each other and there is friction between the two blocks and it's a kinetic friction ( given μk). if i was given the force applied on the lower block to the right direction for example. ignoring the friction between the lower block and the ground, i tried to draw...

Having trouble with something that's likely too trivial, but here goes.. In Optimization theory and nonlinear programming [Sun, Yuan] the following is discussed at section 8.2. Consider the optimisation of f:\mathbb R^n\to\mathbb R with constraints g_j:\mathbb R^n\to\mathbb R, g_j(x) = 0...

Are two objects, accelerating at the same rate, and in the same direction, considered inertial to one another? If so, I will post my resulting question. If not, it's safe to disregard this thread. Thanks, Jake

Homework Statement Forces of 11.8N north, 19.2N east, and 15.9N south are simultaneously applied to a 3.93kg mass as it rests on an air table. What is the magnitude of its acceleration? What is the direction of the acceleration in degrees? (Take east to be 0 degrees and counterclockwise to be...

I had a question about michelson morley and about sr. Did michelson morley show that there is no preferred direction in space only? Is there a preferred direction in time? Seems like in sr, there is no preferred frame of reference, but does this mean that there is no preferred direction in time...

Homework Statement [/B] So here is my question: I asked you about a solution approach/solution for the following task: Two rail paths cross at an angle of 145 °. With a constant speed of 60 km/h, they just drive along their tracks, and each of them repels steam/smoke flags, which, among other...

Homework Statement What is the magnitude and direction of the electric field at the position indicated by the dot in the figure below? Give your answer in component form in the blanks below. What is the x-component of the electric field at the indicated point? Homework Equations kq/r^2 The...

Hi all, I have two questions about light in Special Relativity. (I'm going to pad these questions out with a few statements about my understanding of length contraction and time dilation, so you can see how I currently think about it and clear up any misconceptions if I've got the basic idea...

SR says that there is length contraction in the direction of movement. This works nicely for light going from the back of the ship to the front. From my perspective, the ship is moving away but that is offset by the ship's contraction. But things get tricky for light going from the front of the...

Homework Statement A car traveling at a constant speed of 24.0m/s passes a trooper hidden behind a billboard. One second after the speeding car passes the billboard, the trooper sets off in a chase with a constant acceleration of 3.0m/s^2. A) How long does it take the trooper to overtake the...

Is there a process that can artificially change the direction of photons?

Homework Statement I can't understand why friction acts radially inwards when a body is rotating on a rough turntable. If the friction is removed, the body would move tangentially, hence it has slipping tendency tangential, not radially outwards, then shouldn't friction act tangentially...

Homework Statement Homework EquationsThe Attempt at a Solution I know that, according to the right hand rule, the direction of the field lines for X and Z are anti-clockwise and Y is clockwise. What do I do next? Thank you!

Let's say that we have two guys, each weighs 50 kg. They are pulling a piece of against each other as hard as they can. The tension of the rope will therefore be the force of friction acting on each of them (the same magnitude). Now, let's say that a third person joins the party and grabs the...

Homework Statement A constant potential is maintained across a parallel plate capacitor. A dielectric slab is slowly inserted between the plates (width of slab=distance between the plates). What will the direction of force applied by capacitor on dielectric be? Homework Equations All relevant...

Angular velocity is the rate of angular displacement about an axis. Its direction is determined by right hand rule. According to right hand rule, if you hold the axis with your right hand and rotate the fingers in the direction of motion of the rotating body then thumb will point the direction...

Hello, I'm boy who suddenly been strucked by curiosity on how hand crank generator works and i watch and read some of how to create one, specially this one on youtube: and i want to create one but i don't have a 3D printer, but i saw some alternative but as i do/design my own coil based on...

I am trying to do some calculation based on a k.p model of GaN proposed by S. Chuang [Phys. Rev. B, 54, 2491]. It is a 8 by 8 Kane model with basis functions: The 8 by 8 Hamiltonian contain first order of k is where ##{k_ \pm } = {k_x} \pm i{k_y}## the reciprocal space and high symmetry...

OK, so my last post seemed meaningless. Can anyone help with this, I understand some of you say current moves from the positive terminal of a battery to the negative terminal and some say the opposite. Lets say it is positive to negative just for this question. If I have a battery that the...

Hi all, Can anyone help to solve this problem? Imagine a big plate suspended in the air through three threads with different length. we know length of each individual thread, and they are 120 degree apart from each other. How cam we calculate the tilt of the plate and direction of the tilt?

Watching an old Royal Institution Christmas Lecture, given by Prof. Eric Laithwaite in 1974, there was a demonstration of a simple 3-phase induction motor. As the applied voltage was increased, the direction of spin suddenly reversed at about 203 volts. I have never found an explanation for...

Homework Statement Homework EquationsThe Attempt at a Solution I am having a little doubt as to how to think of the moving electron as a current . I am considering the moving electron as a very tiny (infinitesimal ) current element . It is as if when the electron is at A , there is a very...

Homework Statement There is a magnetic field B=0.02 Tesla and its direction is toward the plane (perpendicular to plane, shown by X X X X X - I'm not sure how to say this direction in English,sorry). we have a copper wire (uniform bar) perpendicular to magnetic field from south to north. we...

I was wondering if it would be feasible to set up something like the following experiment to validate the pilot wave theory. The idea here is to set up a double slit experiment, but control the initial conditions of photons emitted from a source (i.e., their directions) such that one can...

Homework Statement Two charged balls are placed in point A and B and the distance between them is 9,54cm. Each of the balls are charged with 8,0 x 10^-8 C. Find the scalar value and direction of the electric field in point C placed 5 cm from A and 6 cm from B. Homework Equations Cosine Rule...

Outside the battery, in the conductor it is in the direction of conventional current. But what about inside? Since magnetism and electricity are related, and magnetic field inside a magnet is from South to North (outside it is North to South), i doubted for any correspondence.

Homework Statement A rod is attached to a wall in such a way it can swivel. In this case: In which direction does the force (of the wall on the rod) point to? Here are two examples (see under attached files), but the the direction of the force is different. Why? Is maybe one of the pictures...