Position Definition and 1000 Threads

It is one more weekend before I get an official answer for my PhD request... I am totally broken (mentally) and stressed as I am the worst-case-scenario person... In the past, this trait of mine made me reach a point where I said "screw it, if it happens it happens"... unfortunately this time it...

I just transferred to a university with quite a few undergrad research opportunities. My goal is to go to grad school for cosmology after my b.s. in physics, which will come with a minor in mathematics and 18 hours of astronomy and astrophysics courses. My question is, would I benefit from...

Hello! I'm trying to derive the linear velocity vector from the position vector and the angular momentum vector. I've seen on the internet that V = W x R (V,W and R are all vectors and x is the cross product) but I cannot for the life of me derive it! I've tried doing it by writing out the...

Dear all, I'm a bit confused about a 2D problem which I thought had a simple solution... I don't know if I'm correct, so: I have a 2D space, and time. I know the velocity field v(x,y,t). I would like to know where the particle which start at the position x0,y0 at an istant t0 is at a certain...

While proving the Midpoints of the Sides of a Quadrilateral Form a Parallelogram , I got bogged down with position vectors. Let a,b,c and d be the position vectors of A,B,C and D. But where is the origin? Aren't we supposed to locate position of origin?

I recently got my B.S. in Physics and began applying to various entry-level analytical jobs. An investment management firm is going to give me a 3 hour test online. The subjects are as follows: Brokerage Firm Case Study Excel Data Proofing Logic I feel comfortable self studying vlook ups and...

When scientists say the position of a particle or electron cannot be known at the same time as its speed, do they mean the particle's position in reference to jumping from energy levels in a single atom, the position in reference to traveling around the nucleus of an atom, or do they mean...

Homework Statement The position vector of a particle at time t is R=(1-t^2)i+(3t-5t^2)j. Find the time at which P is moving (a) towards the origin (b) away from the origin.[/B] Homework EquationsThe Attempt at a Solution I've thought about this for a while but I've come to the conclusion...

Given the definition of the covariant basis (##Z_{i}##) as follows: $$Z_{i} = \frac{\delta \textbf{R}}{\delta Z^{i}}$$ Then, the derivative of the covariant basis is as follows: $$\frac{\delta Z_{i}}{\delta Z^{j}} = \frac{\delta^2 \textbf{R}}{\delta Z^{i} \delta Z^{j}}$$ Which is also equal...

1. A bicyclist is finishing his repair of a flat tire when his friend rides by at 3.0 m/s. Two seconds later, the bicyclist hops on his bike and accelerates at 2.2m/s^2 until he catches his friend. A) how much time does it take until he catches his friend? B) how far had he traveled in this...

This is not a HW/coursework problem. Just something I randomly thought about. 1. Homework Statement There is a horizontal spring with a mass at the end of it. The mass has an initial velocity V that compresses the spring. Find the equation of motion for this mass without using energy...

So I've been thinking of continuing after my MSc degree to do a PhD. But I have trouble getting a good feel on research groups of quantum optics and nanophotonics in the world. So my situation is: I life in the Netherlands and I have a good feel on most research groups in the country, but I'm...

Homework Statement A baseball pitcher makes a big mistake and throws the ball straight up. If it reaches a maximum height of 15 m. Find the times when the ball was 8.0 m above the ground. I already solved the variables needed Vi= 17 m/s Time the ball spent in the air= 3.5 s average velocity=...

Does a magnet have to penetrate the plane of a coil in order to generate an emf in the coil? Would an emf be obtained if the coil only passes through the magnetic lines of force, without the magnet crossing the plane of the coil? Thank you.

Homework Statement Find the position and acceleration graphs from the velocity graphs given. Homework EquationsThe Attempt at a Solution I'm pretty sure I've gotten some of them correct but I don't know which one I've done wrong.

I know this question has been asked before but I have only found threads for it at an undergraduate's level of understanding and I am just finishing ninth grade. How does the double slit experiment prove superposition? What led me to ask this question, was that, since when you close one slit the...

Hi, I would be interested in the position and the "appearing" of Jupiters red spot over many decades. Here the first question is: What would be the best coordinate system? Jupiters axis of rotation is very stable. So the latitude would be very interesting in my eyes. But: How do we define the...

Do we find out angular momentum for an object from a specific position? Since L= r x mv. R is the distance from the centre of mass. So can I say that angular momentum is 12 for a fixed position 4 metres away from centre of mass having mass of 1 kg and velocity of 3 metres per second north?

Homework Statement Homework EquationsThe Attempt at a Solution I honestly have no clue as to how to go about this question. Am i supposed to find the area under the curve? but how do i do that without y-axis numbers. am i supposed to look at the slopes?

Homework Statement Homework EquationsThe Attempt at a Solution I knew the answer was between A and B, but the inward curves and outward curves on the position time graph confused me , what exactly does it mean? -does A have an increasing velocity and then B has a decreasing velocity? I am...

Homework Statement Problem is as shown in the picture. The answer is meant to be a 4.59mm. Homework Equations Tau=mu(du/dy)The Attempt at a Solution Force (tau) acting on plate from both fluids is equal, as is velocity (du). mu1 (du/dy1) = mu2 (du/dy2) mu1/dy1 = mu2/dy2 (mu2/mu1) *y1 = y2...

There have been many questions on this forum about celestial mechanics in general, and concerning position and velocity in an orbit in particular. So I offer this post as a summary and reference. Here's a method for finding heliocentric position and sun-relative velocity in ecliptic coordinates...

Homework Statement consider an electron traveling away from the origin along the x-axis in the xy plane with initial velocity vi= viî. As it passes through the region x = 0 to x = d, the electron experiences acceleration a = axî + ayj, where ax and ay are constants. For the case vi = 1.80 ✕...

Here is the new thread. Please justify your criticism of my statement.

x = x0 + v0 * t + 1/2 * constant acceleration * t^2 So this is supposed to be very very simple physics, but I still feel like there's a part of this equation I don't fully understand. The first term is the initial position of the body at t=0. The second term is the initial velocity at t=0...

I oscillated a spring attached to a force sensor above a position sensor. The position and force sensors were zeroed at the spring's equilibrium. The graph below was my result. I'm wondering as to why the graph isn't a perfect line. It makes sense that the force applied on the force sensor would...

...Or do they? I read on a book a few years ago that you can spot a conservative force seeing if it depends on the position or not. That means a non conservative force doesn't depend on the position. What is the physical reason for the relationship between a force being conservative and the...

Homework Statement Can anyone verify if I am interpreting and converting the different graphs correctly? I believe that I am on the right track but would really appreciate some confirmation. Thanks! All help is very much appreciated! Homework Equations N/A The Attempt at a...

Homework Statement 40kg girl and 8.4kg sled are 15m apart on the surface of a frozen lake. By means of a rope, girl exerts a horizontal force of 5.2N on the sled, pulling it towards her. How far from the girls initial position do they meet? Homework Equations f=ma The Attempt at a Solution I...

1. Question The speed of an electron is known to be between 6.0×10^6 m/s and 6.7×10^6 m/s . Estimate the uncertainty in its position. Homework Equations ΔpΔx ≥ h/2π (mΔv) Δx ≥ h/2π (Since Δp= mΔv) Δx≥ h/2π(mΔv) h= 6.63*10-34 J*s c= 3.0*108 mass of electron= 9.11*10-31 The Attempt at a...

1. A particle of mass m initially at rest at the origin is acted upon by a force (vector) F = xi+yj+zk. Its position vector after t seconds areI need instructions on solving this

Homework Statement Assume that you are employed by a company that manufactures hydraulic servomechanisms. You have been asked to recommend an electrical method of providing position feedback rather than the mechanical method used at present (pictured below). The demand signal has been chosen...

Homework Statement dv/dt = -βv Integrate to find velocity as a function of time, assume the particle's initial velocity is v0. β is constant v = velocity (not constant) t = time Homework EquationsThe Attempt at a Solution dv = -βvdt ∫dv = -β∫vdt --------> limits of integration for the right...

The equation following (3.80) seems to suggest that the velocity vector ##\vec{\dot{r}}## must always be parallel to the position vector ##\vec{r}##. But clearly this is not true as a particle's velocity can be in any direction. What's wrong?

Homework Statement Find the displacement from the equilibrium position of the particle that is in the distance x=£/12 from the wave source, for the moment t=T/4. The amplitude of the wave is A=0.2 m Homework Equations x=A*cos(wt)=A*cos2*pi/T* t The Attempt at a Solution x=£/12...

Homework Statement for part b , why when t = 0 , x= 0 , why not x =100 ? the author gave that the object drop from height of 100ft at the start of the question. Homework EquationsThe Attempt at a Solution

I feel terrible for even having to ask this. I'm doing A2 at the moment, and we've gone through these sorts of lessons ever since my early AS days. I'm trying to review my notes cos exams are coming soon and I did some questions, and I'm apparently doing them wrong with what the answers are...

Homework Statement I ended up solving the problem as I was typing it up, I am posting what I did anyway as it took so long to type and might be useful to someone else. I am trying to figure out the position representation of a coherent state and it's time evolution. I should be getting a...

what i mean exactly what is the position of Fermi energy for semi conductor materials 1- at the highest of valance band 2- at the mid-way in energy gap like Fermi level at 0 K

Homework Statement see attachment ***indicates correct answer Homework Equations F=ks The Attempt at a Solution I do not understand how this works, and I haven't been able to find any examples of this.

I have some trouble understanding what to do when the effective mass in a heterostructure depends on position. Suppose for example that you have two materials, which are put together such that in one region the kinetic energy is described by one effective mass and in the other region another...

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Let $P = (1,2,-1)$ and $Q = (3,1,0)$. A point $B$ lies on the line segment between $P$ and $Q$. Given that its distance from $P$ is twice its distance from $Q$. Find the position vector of $B$.

Homework Statement Part d) of the question below. Homework Equations We are told NOT to use the ladder technique to find the position operator as that's not covered until our Advanced Quantum Mechanics module next year (I don't even know this technique anyway). I emailed my tutor and he...

Hi everyone, I'm working on a college project this year about mountain bike suspension damping. By trade I'm a mechanical engineer however, I'm required to construct a simple sensor circuit to monitor the performance of the damper I am making. Forgive me if my wording or logic is not quite...

Hello, I recently graduated with my BS in Chemical Engineering, and for the past couple months I have been trying to get my first entry level position and haven't found anything. I've applied online (so far I'm sitting at about 60 applications) and I keep an excel spreadsheet with the company...

***Sorry I meant to say finding time when you have initial velocity and position*** 1. Homework Statement A test rocket is launched by accelerating it along a 200.0-m incline at 1.36 m/s2 starting from rest at point A (the figure (Figure 1) .) The incline rises at 35.0 ∘ above the horizontal...

Homework Statement Hi, I am trying to use the angular velocity and angular position to find the age of the Crab Nebula but my calculations seem to be erroneous. I am supposed to get a number around 800 but I keep getting 5000+ years of age. I'm going to try to be very specific in what I'm...

So this is something that troubled me a bit- in Shankar's PQM, there's an exercise that asks you to find the position expectation value for the harmonic oscillator in a state \psi such that \psi=\frac{1}{\sqrt{2}}(|0\rangle+|1\rangle) Where |n\rangle is the n^{th} energy eigenstate of...

Homework Statement I don't understand how the following works:Homework Equations I follow ## \Delta \nu_0 = \frac{\hbar }{2 m \Delta x_0} ## easily, but then ## \Delta x = \frac{\hbar }{2 m \Delta x_0} t ## ;leaves me puzzled - I understand multiplying through by t, but how does ## \nu_0 t =...