Direction Definition and 999 Threads

I've seen this question come up before and I have an intuitive explanation: In circular motion, the object is being pulled toward the center, so some of its velocity is being imparted from its tangential path toward the center. If its position with reference towards the center is changing...

Can anyone tell me why?

Ok I know this is simple resolving but I'm a bit confused. If we resolve forces in the vertical y direction (as in the attached image), we obtain Rcos(theta)-W=0 and hence Rcos(theta) = W meaning R = W/cos(theta) [where theta = 18 degrees] However, if we resolve forces along the direction of...

Homework Statement Homework Equations Faraday's and Lenz' law. emf = -d(ф)/dt The Attempt at a Solution The current is increasing upwards during that time interval. Thus, by Right-Hand-Rule, the magnetic field goes into the page at the loop. Lenz' law says that the loop's induced emf...

Homework Statement What is the direction of the red ball's angular momentum about the point A? (see figure) Same as the momentum. Out of the page. Zero magnitude. Opposite to the momentum. Same as rA. Into the page. [/B] Homework Equations Angular Momentum[/B] The Attempt at a...

Mathematically, in SHM,why is x'' (acceleration) always in the direction if x increasing? So if he have a simple setup, an elastic spring on a smooth horizontal table, one end attached to a fixed point, the other to a particle. Let's say the fixed point is at the left end of the spring. If we...

Homework Statement A forward force on the axle accelerates a rolling wheel on a horizontal surface. If the wheel does not slide the frictional force of the surface on the wheel is: A. zero B. in the forward direction C. in the backward direction D. in the upward direction E. in the downward...

Can current go either direction in a bjt, mosfet, and jfet? Or are they all usually just one direction? (Especially the jfet. Given the symmetry, I don't see what the difference is between drain and source) Thanks

Homework Statement a) If a spin-1/2 particle is in the up spin state along z, what is the probability that if its spin along the y-direction is measured it will be found to be pointing in the “up” direction along y? (b) Calculate the expectation values of the components of S, i.e. {Sx, Sy...

Hello everybody. If I choose the positive y direction to be vertically downwards, and the positive x direction to be to the right, and take the cross product y cross x, then the direction of the resultant is out of the page (if I draw x and y as lines on paper). The magnitude is yx sin(φ)...

I have just written a program to calculate Legendre Polynomials, finding for Pl+1 using the recursion (l+1)Pl+1 + lPl-1 - (2l+1).x.Pl=0 That is working fine. The next section of the problem is to investigate the recursive polynomial in the reverse direction. I would solve this for Pl-1 in...

Hi everyone, What I understand is that tension only exists if there are two forces pulling on a rope in opposite directions. What I have also read is that due to Newton's third law, the rope actually pulls back with a force equal but opposite to the two applied forces, so the forces look a bit...

I know very little about physics, but I have a question. What are the effects of turning an off road snorkel head backwards (facing the rear of the vehicle)? We on the FJ Cruiser forums are debating, and I thought I would ask the experts :) Some of the concerns/debates include: reduced air...

Hi, If you've got an arbitary magnetic Flux1 and Flux2, traveling in the same or opposite directions, through a core, it doesn't matter with regards to the point on the saturation curve does it? Opposing or in the same direction it'll still be at the same point on the mag curve won't it?Thanks...

Have a look at this link guys: http://ocw.mit.edu/courses/mechanical-engineering/2-016-hydrodynamics-13-012-fall-2005/readings/2005reading2.pdf. Could someone explain the term − 1/2 ρ(b∆x∆z) in equation 2.2? I don't understand how does that represent force on the plane along z-axis.

Homework Statement The armature of a simple motor consists of a square coil and carries a current of 0.55 A just before it starts to move. The coil is positioned perpendicular to a magnetic field. Explain briefly why the current falls below 0.55A once the coil of the motor is rotating...

I have often heard that in quantum mechanics time has no direction. That the physics works the same going backwards in time than forwards. How does the wave function collapse of a particle follow this idea? If we could see time go backwards would we see particles turning back into waves? Is...

Can you have a left handed pion? i.e. it's spin is opposite to its direction of flight

Hi all, So after the wind almost blew me off my bike today, something occurred to me. It goes like this: We all know that if we bike in the same direction as the air does, then we will get a little push and it makes our journey easier. Then suppose we get a little adventurous (reckless people...

Left picture: There are two moving rails that cross at center (red dot) which itself doesn't move. The rails speeds are close to c, so that they are length contracted by factor 10 (roughly 0.995c). There are markings in rails at interval 10 length units in rails rest frame, so the interval is...

Homework Statement Two charges q1 = -7 and q2 = -2, both charges are fixed in place and the distance between them is 2m. Third negative charge q3 is moving along the vertical line that connects two charges. 1) net force acting on q3 = 0; where is the charge located ? 2) If charge q3 is...

The general motion of a rigid body can be considered to be a combination of (i) a motion of its centre of mass about an axis, and (ii) its motion about an instantaneous axis passing through the centre of mass. These axes need not be stationary. Consider, for example, a thin uniform disc welded...

Hey all, I'm stuck on this problem and not sure how to proceed/if I'm in the right direction. Problem: One reference frame N sits at the origin (inertial frame) while another frame, B, describes a disk rolling on a circular ring about the other frame. Picture below (A) find the direction...

We all know that momentum is conserved in a system. But I am confused of one thing. Suppose we have a system containing a wall with very large mass and a ball and use a classical x-y coordinate axis. If I swing the ball at an angle of 45 degrees from the horizontal, upwards to the huge wall...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >[/color] Three point charges are located at the corners of an equilateral triangle as Q1 in the top, charge Q2 in the left corner and charge Q3 in teh right corner. Each leg of the triangle has a...

Hi! I was wondering what happens with Base current direction if NPN BJT works in reverse active mode? In forward active and in saturation mode currents are like this: Collector and emitter currents in reverse active mode would be in opposite direction: :

Hello,im doing a home project. I have an idea to make a venchile which will move back and forward as well as turn. Its something that i will be able to control with control device,if i press forward it goes forward etc. The thing is that i want to make it with linear...

I think I already know the answer to this, but I can't find an easy reliable source online. Does KP predict reaction direction in the same way as KC? i.e. If KP is greater than 1, the reaction favors the products, and if it is less than 1 it favors the reactants? Or is it just that if KP is...

Homework Statement Lorraine steered her boat out of the harbor, heading east. She traveled 500 m to one buoy and then turned north and headed 300 m to another buoy. Jeff also left the harbor from the same point, and traveled 300 m [N] to a buoy, and then went 500 m [E]. a) What is the position...

My understanding is that, in the standard GR BB model, an expanding universe starts with infinite spacetime curvature but zero space curvature; but a collapsing universe ends with a diverging, spagghettifying spatial curvature - very different animals. The LQC bounce however connects, through a...

Homework Statement The speed of a 2 kg object changes from 30 m/s to 40 m/s during a 5 s time interval. During this same time interval, the velocity of the object changes in direction by 90 degrees. What average force was applied during the time interval? Homework Equations impulse = F.t The...

Two forces in addition to its weight are acting on a 10kg mass. What is the magnitude and direction of the net force acting on the mass? I was able to figure out the magnitude, but how do I find the direction? Thanks.

A bomb is released from an airplane flying horizontally at an elevation 1600 ft with a velocity of 294 ft/s. I don't know how to get the magnitude. Will you please help me?

My question is a little more broad than I could make clear in the title but here goes. First of all, to be clear, am I correct in understanding that light behaves in precisely the same way as an electron in the sense that there exists a wave function which evolves according the Schrodinger...

Homework Statement A block of mass m1= 3.70 kg on a frictionless plane inclined at angle θ=30.0° is connected by a cord over a massless, frictionless pulley to a second block of mass m2=2.30 kg. What are (a) the magnitude of the acceleration of each block, (b) the direction of the acceleration...

1. Given that q=+12uc distance=19cm Find Magnitude and direction exerted on point q2. What happens to the force if the distance is tripled?q____________ q2 ____________q3 q1=+12 q2=-2.0q q3=+3.0q distances between point are equidistant.The Attempt at a Solution F=k Q Q/ d^2 F=F+F...

Homework Statement Hi Everyone, I am going to be doing an experiment soon using strain gauges on a beam and I will have to, among other things, calculate the direction of the maximum shear strain with respect to the axis of the beam. I am trying to find the correct equation to use. Homework...

Is the electric force negative when it is in opposite direction as the electric field? If it is, a positive charge would always have a positive E. force? thanks.

*How can I finish off the "only if" direction? I am just unable to prove the only if direction! Using the induction hypothesis and the triangle inequality is confusing me for some reason.* Show that \begin{equation} |z_1+z_2+\dots+z_n| = |z_1| + |z_2| + \dots + |z_n| \end{equation} if and only...

Homework Statement Two parallel wires both carry currents directed from left to right. A circular wire loop lies in the plane of the two wires midway between them. The currents are positive charges. Sketch the changes in the magnetic fields induced and the resultant current direction in the...

So I've been told that the direction that you wind a coil will determine the polarity of the induced voltage across the coil. I drew out two coils with clockwise and counterclockwise winding direction and with using the right hand rule and saying that the positive polarity of the induced...

Homework Statement Find a vector that has the same direction as <-2, 4, 2> but has length 6. Homework Equations Length of vector in 3D = |v| = (x2 + y2 + z2)0.5 The Attempt at a Solution I can see that the length of the given vector is (-2)2 + 42 + 22 = 24 36 is (1.5)24, so I tried...

Homework Statement Block B has acceleration of 4 m/s2... Relative acceleration of block A w/ respect to B is 4 m/s2. Find magnitude & direction of accel for A? Homework Equations a_A = a_B + a_A/B x_A = x_B + x_A/B y_A = y_B + y_A/B The Attempt at a Solution x & y components: -4cos(20) =...

Homework Statement : Block B has acceleration of 4 m/s2... Relative acceleration of block A w/ respect to B is 4 m/s2. Find magnitude & direction of accel for A?[/B] Homework Equations a_A = a_B + a_A/B[/B]The Attempt at a Solution a_A = 4 +4 = 8 m/s2 <-- 8*cos(20) = 7.52 (x-component)...

I currently have an entry level desk job in engineering at a large defense contractor. The work and lifestyle is...very boring...to say the least. Right now my work is not very challenging (I suspect because it is entry level right now, but I have seen people with 5-10 years of experience doing...

I wanted to know why the we calculate the work done of a person climbing up a set of stairs using the y direction,for example, we use the equation w=mgh to calculate the work done for a person climbing up a set of stairs. I do not understand why we are not also calculating the work done in x...

1. The Problem 2. The Free Body Diagram 3. The Question I've always had trouble determining the direction of the vertical and horizontal components in FBDs for statics problems, especially for a pin. Prior to looking at the solution, I wasn't sure on almost all of the directions of the...

I know that normal force is a reaction force. http://www.sumoware.com/images/temp/xzhhpaacgkdktjna.png In the leaning ladder problem, the normal force is perpendicular to the floor and the wall. But, in the cable and beam problem, why isn't the normal force perpendicular to the wall ...

Why is tension at a specific point in a string in 2 directions? For example in the first part of image 1, the string is pulling the two blocks upwards. And in the second part of image 1, the string is pulling the pulley down too. Does tension at a point in a string try to pull the point in 2...

I can't understand this. When I think of a conductor I think of a cable, and last time I checked they are pretty static. So what is this "force" in practical use?