Direction Definition and 999 Threads

A force is given to the center of the object so the object rolls to the right without slipping. I understand that to provide clockwise rotation the static force should be directed to the left. But if the force F is located at the very top of the object, the static friction is directed to the...

I have drawn three free body diagrams, one for each box and then I applied Newton's Second Law after choosing a reference frame rotated clockwise by ##\alpha##, with ##x## pointing south-east and ##y## pointing north-east and I got: ##\begin{cases}m_{1x}: -T+m_1g\sin(\alpha)+F_{fr_{12}}=m_1...

The implication seems to be that from the beginning of the post expansion era, there was everywhere an average velocity of a large volume of matter which was (very near) zero everywhere with respect to a common fixed coordinate system (with a spacially uniform time expansion of distances)...

This may be a weird question, but i was just in the bathroom and had to think about it out of nowhere. I would appreciate any answers!

when a railroad engine wheel slips on a rail as it tries to move forward i can see sparks mostly going in the rear direction. while thinking about what might happen in other situations, such as a moving engine (being pushed by its massive 100 car load, perhaps), i came to a simplistic case that...

The figure illustrates the situation. The radii of the larger and smaller discs are 2R and R, respectively. Their masses are M and 2M, respectively (the largst disc has the smallest mass). Also, m=5/4 M, where m is the mass of the suspended object. The pulley is "massless" (negligible moment...

a. Emily works in the canteen and sells on average 16 Banana milkshakes, 13 baked macaronis, 5 Cauliflower Fried Rices, 25 Blueberry Muffins in one break. Each break at the cafeteria is 30-min-long. How long is it likely to take Emily to sell 50 Banana Milk Shakes, 34 Baked Macaronis, 25...

I have an answer to a partial differential equation. I have the equation coded as followed. I am trying to get this wave to propagate back after it hits a given z value. Can anyone help me figure out the direction in this equation...

Does the electric field vector takes into account the field's radial direction? Usually when we calculate the electric field, we use ##\vec E = \frac{kq}{r^2}\vec j##, which is a straight line vector of a positive charge q's electric field. This electric field points from a positive charge q to...

That was my approach: $$P_f - P_i = [(m-dm)(v + dv) + dm(u+v+dv)] - [m(v)]$$ $$= mdv - dmv + dmu + dmv = mdv + dmu = 0$$ Since the variation of the rocket's velocity is perpendicular to itself, $$ dv = v d \theta => m v d \theta + dm u = 0$$ So we have $$\frac{dm}{m} = \frac{-v d \theta}{u}$$...

Needing Direction I have sets of number: week 9 27 turned in 25 good 2 bad = 93% & 7% week 10 56 turned in 55 good 1 bad = 98% & 2% week 11 75 turned in 74 good 1 bad = 99% & 1% week 12 6 turned in 5...

I've tried to use the 1st equation as a matrix to determine, but it clearly isn't a diagonal matrix. My guess is that I need to find the spin matrix along the direction ##\hat{n}##, but do I need to find the eigenstates of ##\sigma \cdot \hat{n}## first and check if they form a diagonal matrix...

Static friction is known to provide centripetal force when a car turns. Assuming uniform circular motion, my questions are 1. Is the static friction of each wheel points toward the center of turning circle or it's the combined forces of all four wheels that has to point toward the center of...

On the Internet, I have read that the energy doesn't flow in the wire, for example in a very simple electric circuit made of a battery and a closed loop. When one computes the Poynting vector ##\vec S \propto \vec E \times \vec B##, one gets that its direction is towards the center of the wire...

Considering a ferris wheel with the spokes being pretensioned cables. Which directions do the loads vs reactions go?

Using the equations mentioned under this question, I came up with following analysis and directions of velocities on either side of ##x_1##. Also, I'm not sure if there is an easier qualitative way to know the velocity directions rather than do a detailed Calculus based analysis?

Hi, although there is a lot of discussion here in PF, I'd like to ask for a clarification about the definition of 'spatial x direction' in the context of flat or curved spacetime. Consider a set of free-falling gyroscopes (zero proper acceleration) passing through an event A with different...

The second diagram is my attempt at the solution, in which the dotted part is the pulse in the rope a very small interval of time after ##t=0##. Point A should be at rest since we know wave is moving towards right and point A on the rope becomes a part of initial horizontal part of the string a...

For objects traveling north or south, the Coriolis force makes sense. The velocity of the Earth's surface changes with latitude, causing an object to drift east or west relative to the Earth's surface. However, when an object is traveling east or west, the latitude is not changing. How would...

Edit: Ugh accidentally posted instead of previewing, this is a lot of latex to write to give my attempted solution, but I'll keep doing that. I am using the chain rule (or dividing the differential of ##\vec v'## by that of ##t'##). I get $$d \vec v' = \frac{d \vec v \cdot \vec u}{\gamma c^2...

Hello, I am trying to get some intuition about the direction of the shear stress caused by the Hertz contact pressure. Once I exert some pressure downwards on a spherical object the direction of the Hertz pressure will be upwards. However, this case some shear stress to exist, but I can't see...

Could I please ask for help with the following question: The last part follows easily from the first part. Answer from back of book for first part is: 2/(3u') <= tan(Ɵ) <= 2u What I have done is the following: Here's my diagram (I have separated the components to show the internal forces...

ok this was posted on LinkedIn and sure it has already be answered but usually these types of problems are resolved by way too many steps so just wanted to proceed with this without looking at previous attempts my first reaction was to get a CD but would introduce a bigger problem however...

Paper has a grain direction – the direction of the long fibres. For several reasons, publishers always print hardcover books with the grain of the paper in the same direction as the fold. I'm working on a book that will be 2:1 wire bound (two holes to the inch). I was wondering what the grain...

What are intervals of which the function $g(t)=3t^2-5t+1$ a. find the vertex convert to vertex form $g(t)=a(t-h)^2-k$ \item $g(t)=3\left(t-\dfrac{5}{3}t+\left(\dfrac{5}{6}\right)^2\right) +1-\dfrac{25}{12} =3\left(t-\dfrac{5}{6}\right)^2-\dfrac{13}{12}$ b. the parabola opens up and the vertex is...

Please could I ask for help with the following: Here is my diagram, I show the rod displaced from the sphere so as to label the internal forces acting on each of the rod and the sphere: In the diagram below I have added the line through DE at angle ꞷ the the horizontal, and a few other...

So for the first question it is very straight forward. The magnetic field is going through the loop, increasing the flux through the loop. The induced current must flow clockwise in order to generate a field that goes through the loop in a downward direction to oppose the change.The second...

He explain escape velocity in example where rocket goes straight up,isnt escacpe velocity ,velocity where centrifugal forces and gravity are equal,so refers only when rocket going in circle/orbit? Can rocket really leave Earth in straight line like he show in video once reach this velocity and...

I'm trying to find the wavelength. However, I don't understand why the wavelength is different if the wave is moving in the +z direction. I have ##\Psi(z=15cm,t) = \hat{x} 6 cos (\frac{\pi}{3}t)## ##\Psi(z=12cm,t + 2s) = \Psi(z=18cm,t)## For a wave moving on the -z direction I know that the...

Hi, Is it possible to have a transformer/coupled inductors whereby current changes in once coil cause current changes (induction) in another coil but not vice versa? To put it in other words, is it possible to have such a design of a transformer where for example changes in current in primary...

I need to calculate H-bonds in a specific direction of a C-alpha atom of a protein. And, I need to calculate that from a PDB file. Can anyone give me a general guideline/direction/idea regarding how to do that? N.B. I need to write a python program.

This isn’t a HW problem per say, but it’s an example shown in my statics textbook that is used to try an explain that you need to add a couple moment to move a force to a point not on the line of action, and I’m just not seeing how the direction of the couple moment is correct. See the image...

I don't really understand the question. A proton collides obliquely with another proton means that the first proton moves at certain angle with respect to horizontal? This is my sketch: Is that correct? If yes, is it solvable since there are so many unknowns? Thanks

I'm not sure of my answer but it is e(downwards). I arrive at this answer since gravity always exists so no matter what happens it always pulls an object downwards. But I am not sure. Thank you -sun1108

Given a diffeo ##\phi : M \rightarrow M'## (and with ##f## a function on ##M'##), vectors ##X## can be "naturally" pushed forward with ##\phi_*## from ##T_{p}M## to ##T_{\phi(p)}M'## subject to ##\phi_{*}X(f) \bigg{|}_{\phi(p)} = X(\phi^* f) \bigg{|}_{p}##. And 1-forms ##\omega## are naturally...

In this page you can see it’s written: E must be perpendicular to the surface. If it were not then the charges would move due to a component along the surface. I am assuming the field is generated due to the charges on the surface. I have a doubt. Is the author saying if it were not...

The unit vector r roof points in the direction of increasing r with phi fixed; phi roof points in the direction of increasing phi with r fixed. Unlike x roof, the vectors r roof and phi roof change as the position vector r moves. What I was thinking of the image is Although, I was thinking why...

Question:

When the boat moves to the left, water molecules below it also move to the left. Is it correct to say the reason is because of Newton's 3rd law? Water molecules provide friction force to the boat so force on boat by water molecules is to the right. By Newton's 3rd law, there will be force on...

If I use the expression ##(|A\rangle+|B\rangle)|M\rangle \rightarrow |A\rangle|M_A\rangle+|B\rangle|M_B\rangle## for decoherence, does that mean that we can infer that, IF the measured value is ##A## that THEN we will measure ##M_A##, OR that IF we measure ##M_A## THEN the measured value must...

I don't understand why they said that the induced current flow is opposite to each other when it clearly states direction is to the right for both? https://www.physicsforums.com/attachments/285900

Nevermind I found what I had to do, thank you though.

From the relevant equation above, there is not imaginary part in the |+> state, so I multiplied the state by (1-i). The state is then : ##\Psi=(2)|+>-(1+\sqrt{3})+i(\sqrt{3}-1)|->## Then I normalize it : ##\Psi=(\frac{1}{\sqrt{3}})|+>-\frac{1}{2\sqrt{3}}(1+\sqrt{3})+i(\sqrt{3}-1)|->## From the...

in my worksheet, AB turns in clockwise direction , while in my textbook, it turns in the anti clockwise direction. so may I know why is this the case?

This is one more thread in my quest to learn simulations in LTspice. I am trying to simulate the gain limiter network shown in this video. A snapshot of the video is available for quick reference: My schematic in LTspice is shown below: For the simulation, I am using DC sweep on voltage...

The following is my work: The following is the answer given: While I took FA as the pivot point, the answer seem to have taken FB as the pivot point, and got negative value for FB. As the result, the answer seems to have used the tensile strength for FA and compressive strength for FB...

I understand that negative charges create electric fields pointing inwards, and positive charges create electric fields pointing outwards, but what does this have to do with field stength? What is the relationship between field strength (flux?) and direction?