Direction Definition and 999 Threads

if i have rod of a certain length. let point (a) on one end of the rod and point (b) on the other end. along the rod axially is the X axis, vertically Y axis and Z is the lateral direction.let force prependicular on x -axis at point (b) and move this force to point (a) which will create a...

Hello all - a quick question that I can't seem to find an answer to online that I trust... While the conventional current model describes flow of positive charges around a circuit, we know that current is actually the flow of electrons (at least in common metallic conductors). Which leads to...

What I'm wondering is whether or not the E-fields and B-fields making up an EM wave always point outwards. Would it be possible to have an EM wave where either the E-fields or B-fields, or both, point inwards towards the path of propagation? The only diagrams I see in books and the internet...

Homework Statement Hi All, this problem is related to spin-1/2 in an arbitrary direction, in particular building off of, but going beyond, Griffiths QM 4.30. I am given an unnormalized general spin state, \chi in the z basis, and then asked "in what direction is the spin state pointing?"...

Homework Statement To protect their young in the nest, peregrine falcons will fly into birds of prey (such as ravens) at high speed. In one such episode, a 600g falcon flying at 20.0m/s hit a 1.40kg raven flying at 8.0m/s. The falcon hit the raven at right angles to its original path and...

I recently had this idea (which perhaps is not a new one, but I have never heard of it), that on the scale of the entire universe, time expands in all directions at once. I believe it can be proven or disproven with more knowledge, so I am posting it here. If we look around us, we generally...

I see textbooks assign directions to magnetic field lines, for example north poles extending outward and south flowing inward. Are these directions correct or just a way to help tie the concept together and have just been arbitrarily picked much in the same way as conventional current?

Homework Statement If we have an electric field with a positive and negative plate: The field lines will be going from the positive to the negative, so down. But, if we put an electron between these two plates, it will be attracted to the positive plates, so it will have a force vector...

The electric field direction can be measured by the force affected on a test charge. Let's put a point-like charge not far from a material, that is polarized by it. See the figure: The test force on the test charge A points exactly to the charge. I think that because the surface is...

The direction of Earth's magnetic field in the northern hemisphere is downward and to the north. If an east-west wire moves from north to south, in which direction does the current flow? I have no idea how to approach this problem. It was on my physics test and I got it wrong and I'm doing...

Direction of current in the figure?? Homework Statement What must the emf in the figure be in order for the current through the 7.00-ohm resistor to be 1.76A? Each emf source has negligible internal resistance. Figure...

All, please help me refine, restate, explain, understand, expand, add, remove, answer the below statements/ questions. Thanks in advance. 1.) Voltage is considered a scalar quantity. (J/C in SI Derived Units) which is a magnitude of energy per coulomb...no direction with this example. Some...

Homework Statement Find all the points at which the direction of the fastest rate of change of the function f(x,y)=x^{2}+y^{2}-2x-4y is i+j Homework Equations The Attempt at a Solution The direction of the fastest change is \nabla f(x,y)=(2x-2)i+(2y-4)j, so we need to find all...

Suppose we have a thick slab with a current density J pointing strictly in x direction...see below link for figure: http://teacher.pas.rochester.edu/PHY217/LectureNotes/Chapter5/LectureNotesChapter5056.jpg what is direction of magnetic field inside? It is easy for me to see that...

Homework Statement http://img805.imageshack.us/img805/6030/82154948.png Find Vemf (between points 1 and 2) and it's polarity at t = 0. I have omitted details because my question is specifically on the polarity.Homework Equations Lenz's law: An induced electromotive force (emf) always gives...

Hello, I know about the right hand rule, but I get confused when velocity and magnetic field are not perpendicular to each other, then how do I determine the direction of the magnetic force? Can I not use the right hand rule?

Homework Statement Three vectors, A, B and C each have a magnitude of 50 units. Their directions relative to the positive direction of the x-axis are 20°, 160° and 270°, respectively. Calculate the magnitude and direction of each of the following vectors. 1.) A + B + C 2.) A-B+C 3.)...

Reflection/refraction of light is due to the absorption of photons by electrons in the governing atoms, and is then reflected/refracted with a different wavelength and direction. I understand why the light might be a different colour (wavelength), but I don't understand what causes the incident...

Pre-theoretically, we notice that objects have some property responsible for their varying dispositions to resist being pushed around in space, or to resist changes in motion given applied forces ("inertia"). So we introduce the term "inertial mass" to apply to the most physically interesting...

Homework Statement Find the force on 7.0 cm of conductor bearing a current of 6A if it lies perpendicular to a magnetic field of intensity 1.2 T and the wire makes an angle of 60° with the magnetic field? Homework Equations F = IlB sin θ The Attempt at a Solution The magnetic force...

Homework Statement #45 What is the magnitude and the direction of the current? Homework Equations The Attempt at a Solution I know how to get the magnitude but i don't get the current direction...how do i find out which way the current goes? What is the general rule to find the direction of...

So let's say we have a red light wave, can you have something particularly simple amplify it's wavelength, I know you could take a picture of it and send it out again the opposite side, but that's far sought. Oh and if an electromagnetic wave is absorbed by an atom, how exactly do you tell the...

Homework Statement Why does friction act towards the center when a car does uniform circular motion by itself. The Attempt at a Solution I know that centripetal force is needed to move an object in a centre and so there should be a force acting towards the center in the circular...

Homework Statement This i the usual lifegard problem: we have a lifeguar that has a soil and water velocity, and wants to rescue a person at position (x,y). The lifeguard is ate the origin and th beach ends at position l, he wants to reach destination aa fast as possible. We all know that...

Hi, Consider a ball rolling upward without slipping on an inclined plane. What is the direction of the force of static friction? Let me explain what confuses me. I know that the friction opposes the tendency of the motion. If we consider the whole motion of the ball as upward, then the...

sorry, this is is a general question about a conceptual definition I read in my textbook, i hope that's ok. "an object that rolls without slipping at a constant velocity over a surface with friction experiences no frictional force" is this true? i understand that on a frictionless surface, the...

Hi all, Is it possible to find the direction of a source in 4 quadrants using directional antenna? I am thinking of setting up 4 directional antennas, facing to 4 quadrants, and they will receive the waves from the according quadrants. What do you guys think about this? And is there any...

Homework Statement A bus traveling at 65km/h on a bearing of 190° changes direction to south-east and continues at the same speed. Find the change in velocity of the bus. Homework Equations The Attempt at a Solution I'm fairly hopeless at drawing the diagrams for these questions so I...

In the attached picture, one sees a pulley with a mass which is holding two different weights. In chegg, the tension due to a weight is represented as a downward direction. Then, when the tension is seen in relation to the pulley, the direction switches for both weights. WHY IS THIS...

I heard this question from my TA and was not satisfied with the answer. Can someone elaborate for me please? There are two infinite lines of current that are traveling in the same direction. By the right hand rule and ampere's law, we can calculate the magnetic field and calculate the F of...

hello friends, a ball experiences uniform motion due to inertia and gravitational force which is acting downwards. Both these forces are perpendicular. So given these conditions,in which direction the ball will move? I think with the help of trigonometry we can solve this.. Since there are...

Homework Statement if f(x,y,z) indicates electrical charge in the water at position(x,y,z) and the gradient is <12,-20,5>, in which direction should the shark swim to find its prey? Homework Equations The Attempt at a Solution is the answer in the direction of <12,-20,5> im...

Homework Statement surface of mountain is modeled by h(x,y)=5000-0.001x^2-.004y^2. Climber is at (500,300,4390) and he drops bottle which is at (300,450,4100) What is his elevation rate of change if he heads for the bottle? In what direction should he proceed to reach z=4100 feet the...

Please help! Calculating the direction of Earth's magnetic field Homework Statement Calculate the direction of Earth's magnetic field. Homework Equations The Attempt at a Solution 3 components of the magnetic field: Geographic South to North: 0.01670 mT Geographic West to...

When solving the three dimensional Schrödinger equation, we obtain a probability distribution on θ. But it seems like the procudure produces a particular direction the z-axis. While the Coulomb field is spherical symmetric, it shouldn't exist such a preferred direction. I'm puzzled.

Homework Statement A 55kg man is running in the positive y direction at 4 m/s. He is tackled by a 115kg man running 8.5 m/s at a 140 degree angle. What is the speed and direction after the inelastic collision? Homework Equations p=mv p = sqrt of x^2 + y^2 The Attempt at a Solution...

In each of parts (a), (b), and (c) of the figure below, find the direction of the current in the wire that would produce a magnetic field directed as shown. part (a) right to left part (b) out of the page part (c) lower left to upper right Ughhhhh So, the right hand rule...

2. Three loops of wire move near a long straight wire carrying a current as in the following figure. (a) What is the direction of the induced current, if any, in loop A? a. clockwise b. counterclockwise c. No current is induced. (ANSWER) WHY IS "C" THE ANSWER? I don't understand...

Homework Statement A linearly-polarized electromagnetic wave with a frequency w and with an intensity of 1MW/cm2 is propagating in x-direction in a nonlinear crystal with a refractive index n=1.5. Assume that a second-order nonlinear optical susceptibility tensor for second-harmonic...

Homework Statement Tim is running cross country at 6.4m/s[S] when he completes a wide angle turn and continues at 5.8m/s[w]. What is his change in velocity? Homework Equations Δv=v2-v1 a2+b2=c2 The Attempt at a Solution i am not sure how i am supposed to find the change in...

I'm studying rotational dynamics and I've got a couple questions I can't answer. I want to describe de movement of the bodies in the cases below, the coefficient of friction in all the cases is \mu . I will say what I think it would happen, and I would appreciate if you guys judge it right or...

When constructing a simple circuit with a battery, bulb and a switch, the placement of the battery is unimportant (I can hook up the battery + then - or - then +). So why is it that so many battery powered electronic devices only work if the batteries are inserted in a specific direction?

Homework Statement if we apply a force of 56 n on 40 degree angle above the horizontal than how would the results compare if it was applied 40 degree below the horizontal?Homework Equations none The Attempt at a Solution i said that it would be the same and different depending on how we look...

Homework Statement A plank of mass M is placed over smooth inclined plane and a sphere is placed on the plank as shown (see attachment). There is sufficient friction between sphere and plank to prevent slipping. If system is released from rest, the frictional force on the sphere is a)up the...

Hey yall. This is a question from my homework but it's so basic that it's just to help with the concept for me. So the question is this: A small object A, electrically charged, creates an electric field. At a point P located 0.250 directly north of A, the field has a value of 40.0 directed to...

I hope that this is a foolish question and that someone can make quick meat out of it. If \gamma: S^1 \to M is a loop on an arbitrary manifold M, our goal is to analyze the tangent vectors to \gamma when the loop is traversed in the opposite direction. Let \iota: S^1 \to S^1 be the map...

Homework Statement A pilot needs to fly his plane to a location due east as fast as possible. The plane is capable of flying at a top speed of 140 km/h in still air. In this case the wind is blowing exactly NE at 42.5 km/h. In which direction should the pilot point the plane? What will be the...

Homework Statement Two long, parallel wires carry currents of I1 = 2.78 A and I2 = 4.80 A in the direction indicated in the figure below. (Choose the line running from wire 1 to wire 2 as the positive x-direction and the line running upward as the positive y-direction.) a) Find the magnitude...

Homework Statement A boat can go 12 km /h in a river that has current of 5 km /h. At what angle relative to the shore does the boat have to leave to arrive directly across from initial location? Homework Equations SOH CAH TOA The Attempt at a Solution I just want some...