Direction Definition and 999 Threads

I am interested in ultrafast optical spectroscopy of solid state materials. The unique measurements and especially the process of developing new measurement tools for the optical measurement of quantities that are hard to measure in other ways, and the learning of transferrable skills, make this...

Homework Statement John jumps and shoots and makes a basket from the far end of the court, a distance of 27.5 m. The ball is shot at an angle of 41.0 degrees to the horizontal from a height of 1.98 m above the ground with a speed of 17.2 m/s. The basket is 3.00 m off the ground. a. Sketch a y...

Consider the three displacement vectors A with arrow = (-4i hat bold − 3j hat bold) m, B with arrow = (6i hat bold − 8j hat bold) m, and C with arrow = (-3i hat bold + 5j hat bold) m. Use the component method to determine the following. (a) The magnitude and direction of the vector D arrowbold...

Homework Statement Homework Equations An = mv^2 / r The Attempt at a Solution I get the 2D free body diagram, and how the vertical components are resolved, but how is Nc sin θ = mv^2 / r when they both are in the same direction? Also another related problem is this diagram...

I have a simple question... does the magnetic field angle of direction vary when you vary the field strength? For example, say i have a magnetoresistive sensor, which, to my knowledge only detects the magnetic field angle of direction (unlike a halls, which senses field strength). I place...

Hello everyone! I'm going to uni in October and I'm brushing up on my mechanics before I go. I've just got to a bit that has confused me before and has confused me again now: When you have a rotating object, say it is rotating in front of you in a vertical plane and it is rotating...

I have a big confusion. There is a question in my book which basically says that a ball is tied to a string and rotated. and it asks me to tell whether the following statement is true of false. Direction of radial acceleration MAY remain the same. This statement is true. Please explain to me a...

I have a simple question let's say object hits the wall at angle and reflect. Will reaction force from that impact exerted on wall be red line or green line ? ( I would like explanation why in each case)

Hello All, I am a self learner. Since my childhood days I was fascinated with physics, relativity, quantum physics. I started reading some popular science books and then found that without a background of mathematics it is all unrevealed romanticism. Let me tell you frankly, I am a commerce...

In the attached figure, a de-energizing RL circuit is drawn (left switch is opened while right switch is closed). In the drawing the voltage induced in the inductor is put to be negative so that the math works out. However, that would be against Lenz's law, wouldn't it? The inductor should be...

Homework Statement I have a problem in a statics class that asks to find the component of a force acting along an axis seen here http://i.imgur.com/aZ1vMIu.jpg?1. Homework Equations The Attempt at a Solution The book and my professor say to use the parallelogram rule and then use...

Homework Statement Can you explain why the for Y , the direction of reflection is in and out of page ? p/s : the wording is in the photo. so i think it's needless to retype it again . Homework Equations The Attempt at a Solution is it because for reflected ray, the ray will...

Homework Statement i can't understand why the reflected light has the direction of oscillating inside and outside of the page while the direction of refracted wave is upwards and downwards (perpendicuar to the plane of wave propagation. ) Can the direction of reflected light vibrate...

Homework Statement Instructions for finding a buried treasure include the following: Go 572.7 paces at 223◦, turn to 156◦ and walk 124 paces, then travel 417 paces at 242◦ I have already found the magnitude...1015.66 paces Now I need to find the resultant displacement... What is the...

Hello guys, I've had the following discussion at work: We are currently using a suture with a nylon thread on a tissue, when the thread of the suture is tightened in a force equal to if we've put a 500 gram weight on both ends of the suture line (meaning both end are tied together to the...

Everywhere I read about the angular momentum / spin of electrons and how a 1/2 spin particle has a unique characteristic that you need to turn it 720 degrees in order to get it turned back to where it was before you started turning it. How exactly do people "turn" an electron in this fashion...

Homework Statement One surface moves over the other stationary surface. a. Is friction felt by both the surfaces? b. Is the friction force same in magnitude? c. What are the direction of friction forces felt by them? Homework Equations The Attempt at a Solution Since both...

Mass-less particles travel at the speed of light. If such a particle has an intrinsic spin, the DIRECTION of the spin angular momentum vector must be in the same direction as the linear motion of the particle. Why exactly is that? Thanks in advance.

Okay, so I'm working linearly through Fundamentals of Electric Circuits and this is a practice problem. Homework Statement Obtain the node voltages in the circuit. http://i2.minus.com/iJPUlZbuy0mLa.jpg The answer is -6 volts for node 1 and -42 volts for node 2. (Which I checked in a...

Homework Statement Calculate the magnitude and direction of the electric field at point Z in Figure 13, due to the charged spheres at points X and Y. Homework Equations E = kq1/r^2 The Attempt at a Solution Determine each vector component: Ex = (9.0x10^9 Nm^2/C^2)(50.0 x...

Quick question. If the EM field vectors are perpendicular to the direction that an EM wave is traveling, how can light push objects away from the light source, such as in the use of a solar sail?

I want to know the current direction in the circuit. From where to where it will flow. I know the simplification of the circuit. All the three resistor will be in parallel. But without simplification of circuit. I want to know the direction of current.

Definition/Summary The direction of the force of dynamic friction is along the plane of contact, and is opposite to the direction of relative motion. The direction of the force of static friction is along the plane of contact, and is opposite to the direction in which there would be...

anyone know how to do it? how to graph differential equations along with the slope/direction field? (Wondering)

Sketch a direction field for the differential equation. Then use it to sketch three solution curves. $y'=x-y+1$ I really need help drawing this, I'm super confused. :confused:

Homework Statement Can an object with constant acceleration reverse its direction of travel? Can it reverse its direction twice? Homework Equations Basic kinematics. The Attempt at a Solution First I thought that it is not possible to reverse direction because if direction...

I was looking for information on how the photo electrons are emitted when under X-ray radiation. In this ancient review paper here http://journals.aps.org/pr/pdf/10.1103/PhysRev.30.488 they state that the most common angles for non polarized X-ray beams (of various energies) range roughly at...

1. Homework Statement [/b] In the figure, two parallel wires carry a current I in opposite directions. A rectangular loop is midway between the wires. The current I is decreasing. The induced current through the resistor R is: A: Zero B: from b to a C: from a to b Homework Equations...

I've never really studied clouds or the movements of clouds or paid any attention to the science that I was taught in school, so if this question seems stupid, I'm sorry. I always watch the clouds from my window and they always go the same way, but today they are going the opposite direction...

The electric field in some region is found to have a constant direction . What you coclude about the charge in the region...?? How can I draw the electric field lines..?? :/

So I'm trying to figure out something I don't understand about the direction of radiation when a charge is accelerated. I know that when a charge is accelerated it gives off EM radiation, which I kind of picture as the electric field of the charge 'wiggling' spherically all around it. If that...

Yes, curious about that. (No, I'm NOT asking about some short term disturbances when glaciers were melting, but whether with lower temperature and part of continental shelf above water caused the currents to change their direction)

When the Lorentz force is applied on a wire that has current flowing in a magnetic field, by changing the direction of the electron(not it's KE) would this possibly change the direction of the Lorentz force? Can the wire be controlled in a way that the force's direction stays the same path?

This thing has confused me for long .I have not come across any satisfactory answers on my own or while browsing through the internet. Everybody has seen the example of a rod moving while on parallel rails, with magnetic field perpendicular to the plane of loop formed by rod and rails...

Hi, I was looking at this picture. I can't seem to get the right hand rule to work. I put my thumb on vector r and my index on vector F. My middle finger points INTO the page!

I'm not sure what "differential" geometry is, so hopefully this is the right section. I need to find the point on a cone that is farthest in a given direction. This can be done easily if the shape were a sphere which is represented as a point and a radius: farthest_point = sphere_origin +...

In my book it says that the Lorentz group O(3,1) includes 'discrete reversals of the time direction'. What on Earth does this mean? So I get that time reversal is making time go backward instead of forward, but what is the word 'discrete' doing there? Thanks in advance!

I'm learning AC and theory says that the polarity of AC inverses.. even the name says 'alternating current'.. now what about the live and neutral? does the current goes from neutral to live and and vice versa? Some people says that only the phase inverses, but the current is always from live to...

Hey everyone, Last summer I had realized that my interest in science had spiked dramatically, and more specifically, the cosmos and physics, so I decided to research the available colleges around me and decided to start off at a community college to take the entry level courses to see if my...

When a body is held or rests in equilibrium in contact with a surface (e.g. a slope, the edge of a block etc.) how do we work out which direction the friction acts in? I'm used to the friction acting parallel to the surface i.e. slope but in one question I have, of a beam resting on the edge of...

Homework Statement At one instant a bicyclist is 60 m due east of a park’s flagpole, going south at 20 m/s. Then 30 s later, the cyclist is 40 m due north of the flagpole, going due east with a speed of 10 m/s. On an XY-coordinate system with the flagpole at the origin, for the cyclist in this...

Homework Statement The right side of a wire loop is dragged to the left across the south pole of a magnet. What will be the direction of the current induced in the loop? a. No current will flow around loop. b. Current will move in the wires of the loop in the same direction as the loop...

Which of the following statements are true?? OPTIONS: A)a rotating ball is kept on a rough inclined plane.It may remain at rest till it is rotating. B)A rigid body rolls up an inclined plane without sliding. The friction force on it will be upwards. C)A rigid body rolls down an...

I have read numerous explanations as to why it is beneficial to launch a rocket in the eastern direction. I know that it's true because NASA's website http://spaceplace.nasa.gov/launch-windows/en/ even claims this. But it makes absolutely no sense to me. I understand that the Earth is...

http://ocw.mit.edu/courses/physics/8-02sc-physics-ii-electricity-and-magnetism-fall-2010/faradays-law-1/faradays-law/MIT8_02SC_challenge_sol21.pdf In problem 8 b), they say the magnetic force must cancel with gravity. How do you determine which way the magnetic force is? I don't...

I now have a general understanding of relativity but it threw up a few issues. I understand that there are no 'fixed' points of reference in the universe, which of course begs the question as to why inertia exists. The way I imagine it is if I am the only matter in the universe, then why should...

Hi guys, As you can probably tell this is my first post, so I thought I ask a question that I've had trouble getting my head round. I think I know the reason but I'm not a 100% certain. Why is it that we see the CMB radiation from every direction we look? I would really appreciate if...

Hello Physics Forums :), My name is Justin. So I am looking for some honest advice and some direction. I am going to give a run down of myself so that way giving advice will be easier maybe? I am a veteran on the GI bill if that matters at all. Also being from Texas, when my 36 months of GI...

Homework Statement A) You travel north down a road in a car at constant velocity. In which direction (N, S, E, W, up, down) does the angular momentum vector point for one of the tires. B) Same situation. If you slam on the brakes in which direction does the angular acceleration vector...

Hello! I've got a question concerning the direction of the vector r in the Feynman Lectures of Physics in Chapter 13.3 http://www.feynmanlectures.caltech.edu/I_13.html#Ch13-S3 Which direction does the vector r in equation 13.5 point in? The long equation before equation 13.6 suggests that it...