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0answers
27 views

Magnetic forces and generators

i'm really struggling to break this question down into manageable chunks and identify which quantities are relevant. I'm also unsure of some of the wording in the question. A bar of length ...
2
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2answers
78 views

Potential and kinetic energy on spherical surface

A small particle of mass $m$ is atop of a semi-sphere as shown in the figure. A little push was given to the particle. Prove that the particle will leave the spherical surface at a height of ...
-1
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0answers
18 views

Isochoric process - need help with a task [closed]

I'm a student and today I saw a task in my book: During an isochoric process, the temprature T increases with 100 Kelvins, while pressure ...
0
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1answer
35 views

Coefficient of expansion [closed]

At a temperature of 21.80°C the hole in a steel plate has a diameter of 1.040 cm. If a steel rod with a diameter of 1.049 cm has to just slip through this hole, to what temperature should the plate be ...
0
votes
2answers
97 views

Is it possible to calculate how fast something will roll down a hill?

If I have a wheel, I know it's mass and diameter and the slope of a hill. Can I calculate the time it will take to get to the bottom of the hill? I am doing a project for my science fair and I sent 5 ...
0
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1answer
144 views

Electric field from current without Maxwell's law of induction

A long, straight wire carries a current that decreases linearly with time. What is the direction of the induced electric field outside the wire? I would interpret this as follows: A current induces ...
4
votes
4answers
257 views

Blocks stacked on an incline connected by rope around pulley

Two objects A and B, of masses 5 kg and 20 kg respectively, are connected by a massless string passing over a frictionless pulley at the top of an inclined plane, as shown in the figure. The ...
1
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1answer
79 views

Acceleration of particles in a pipe with variable cross section

I am currently making an exercise from Paterson,1983, IV.3.ii. It goes as follows Water flows steadily and incompressibly along a pipe whose area cross section $A(x)$ varies slowly with the ...
2
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0answers
41 views

Is my method of calculating thermal conductivity of a metal wrong?

I am trying to determine the thermal conductivity of pure copper at various temperatures using the Weidemann-Franz Law but for some reason it is not matching up to textbook data. I used the Bloch ...
1
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1answer
35 views

Help understanding the solution to a problem regarding kinetic energy of a group of point charges

The problem provided by my professor goes as follows: "Now consider a situation in which all charges are equal to q and they simultaneously become "unglued". What speed will each charge have when a ...
-4
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0answers
39 views

How can I solve this question? [closed]

I tried using the equations dsin(theta)= n*wavelength
-2
votes
0answers
36 views

Free particle in a box [closed]

A particle of mass $m$ is confined in a one dimensional box of width $a$ is known to be in the second excited state. Suddenly, the width of the box is doubled without disturbing the state of the ...
0
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2answers
38 views

Energy realized in fusion and electrons?

I was doing this question about the energy released in a fusion reaction: In the mark scheme it included the mass of the electrons (for part cii) on the left and just used the mass of protons for ...
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1answer
26 views

How to calculate Acceleration

Assume you are moving 10 meters in 10 seconds northward. What is the acceleration?. Using this equation: $a = (v_f - v_o)/\Delta(t)$ and filling it in with this data: $v_f=1$ which comes from $10$ ...
-2
votes
0answers
24 views

Speed and velocity. scalers and vectors [closed]

the roadrunner is trying his best to get away from the coyote, he has travelled 350m {W} in 15 seconds and is now out of the coyotes reach. determine the following the roadrunners speed and velocity
-3
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0answers
25 views

Distance, speed, velocity, displacement [closed]

a motorcyle travels 400km{N} and then 750km{S} in 4 hours. calculate the the following distance , displacement, speed ,and the velocity of the motorcycle
-2
votes
1answer
37 views

How do you calculate the velocity for this? [closed]

I understand velocity is the displacement over time, but I'm having a hard time finding out the displacement of this object. It's moving $10m\:N$, $3m\:E$, and $6m\:S$ in $10$ seconds. What is the ...
0
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1answer
26 views

Variance of Kinetic Energy Operator

I am asked to calculate the variance of the kinetic energy in the ground state of the harmonic oscillator. That requires $\langle T^2\rangle$. This is the same as $\langle p^4\rangle$. My question ...
0
votes
3answers
256 views

Calculating the torque at a point when a motor is stopped?

So, I'm trying to solve for the torque $\tau_A$ of a motor. I have attached a strong stick to the motor, like so: I apply a force $F$ on the stick which stops the motor. The distance from the ...
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1answer
34 views

Expectation of dipole is vector in x direction

So I am asked to find a state $|\Psi(t)\rangle$ in terms of the hydrogen wave functions, such that the expectation of the dipole operator -$e\hat r$ is a vector in the x direction. I am not ...
-3
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0answers
62 views

Two problems related to gravity [closed]

Can someone help me with this 2 problems: Determine the potential of the gravitational field at height 33600km. The radius of the Earth taken 6370km. Two objects with same mass on the time of lunar ...
0
votes
1answer
51 views

Calculting the magnetic field from rectangular conductor?

I want to apply the Biot-Savart law to calculate the magnetic field at a point created by current flowing through a square/rectangular conductor. More specifically, a trace on a printed circuit board. ...
3
votes
2answers
66 views

Locations of destructive interference for two spherical waves

I have looked at this, but it did not help with locations. Really this just comes down to mathematical manipulation, which for some reason I fail to see. Here is my paraphrased setup: Consider two ...
0
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0answers
27 views

Derive an expression for the avg reading (in Newtons) displayed on a gauge [closed]

A solid stream of spheres ($N = 250$ spheres per second, $m = .03kg$ per sphere) rolls off a ledge with a horizontal speed ($v = 1m/s$), and falls ($H = .42m$) onto a level steel surface ($M = 3kg$) ...
0
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1answer
32 views

Ground state degeneration

I wonder how can i know degeneration of ground state of certain elements? I'm doing Boltzmann distribution problems, and I'm not sure what to do. I have to calculate ratio of ions in 3p excited state, ...
0
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2answers
51 views

Collision of two balls of finite radius [duplicate]

This is your typical elastic collision problem except the balls have finite radius. To be clear: two billiard balls in the plane each with radius $\sigma$ move at constant velocities $v_1, v_2$ ...
0
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0answers
6 views

Phasor Diagram with AC circuits [migrated]

Suppose you take a 2.0×102 resistor and a 0.40 inductor and make a series circuit with a voltage source that has voltage amplitude 30 and an angular frequency of 2.5×102 . **Part F (The part that I ...
3
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1answer
89 views

Pipe in a flowing river problem

I'm working on a certain problem in fluid mechanics, which isn't really my strongest area. The problem is as follows: Curved pipe is partially submerged in a flowing river so that one end is pointing ...
-1
votes
0answers
19 views

Calculating Accelerating voltage [closed]

Struggling with this: 2 elementary particles are accelerated in an electric field. They are opposite particles to each other (same mass & wavelength) but opposite charges. They leave the field ...
0
votes
1answer
66 views

Question on Quantum Harmonic Oscillator

My textbook claims that the uncertainty in position of the particle in a quantum harmonic oscillator is $\frac{A}{\sqrt{2}}$ and the uncertainty in the particle momentum is $\frac{p}{\sqrt{2}}$ ...
0
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0answers
13 views

Discharge on the surface of a Van de Graaff Generator [closed]

I have the following questions about a Van de Graaff Generator: What is the minimum voltage needed on the surface for spontanious discharge? What is the charge at the surface with that voltage? You ...
2
votes
2answers
98 views

Changing vector basis in AdS_3

I have AdS${}_3$ given as a surface embedded in a 4 dimensional pseudo-Riemannian space $$x^2+y^2-u^2-y^2=-l^2$$ With metric: $$ds^2=dx^2+dy^2-du^2-dv^2$$ I have Killing vectors of that space ...
0
votes
3answers
159 views

Pendulum (highschool)

I have a question concerning pendulum. On our physics lessons we built simple pendulum consisting of weight and a thread ($\ell=0.31$ m). We tried to calculate $g$ from the well known formula $$T_m ...
0
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1answer
120 views

Doubt in question related to optics---magnification?

Ok here is the question given in my text-book Find the distance of the object from a concave mirror of focal length 10 cm so that image size is 4 times the size of the object. The solution in my ...
1
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1answer
62 views

What is wrong with this derivation of moment of inertia of a sphere?

I know the moment of inertia of a solid sphere is $\frac 2 5 MR^2$, but I keep getting $\frac 3 5 MR^2$ when deriving it: For a sphere of mass $M$ and radius $R$, $$\rho = \frac {M}{\frac 4 3\pi ...
0
votes
1answer
37 views

Freshman year forces problem [closed]

I have been sitting with this problem for about 2 hours now. I know it involves simultaneous equations of some sort... I am trying to figure out maybe if there was not enough information given .. ...
0
votes
1answer
77 views

photon polarization, uncertainty in Energy

A beam of red light is sent along the $z$ axis through a polaroid filter that passes only $x$ polarized light. The beam is initially polarized at $30$°, and the total energy is $10$ Joules. Estimate ...
0
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1answer
42 views

Finding friction forces of stacked boxes on a table

Consider the following system. The given friction coefficients are for static. Let $g=10$ (meter per square second). If the $F(t)=10t$, for example, determine the friction forces $f_{AB}(t)$ ...
2
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0answers
366 views

kinetic energy in collisions [closed]

We were hoping you could help us understand collision energy. Vehicle $ A $ is driving West at $35\space mph$ and weighs $ 1437 \space kg$. Vehicle $ B $ is driving North at $35\space mph$ and weighs ...
-1
votes
0answers
36 views

General wave equation derived from Maxwell's equation

I need to derive the general wave equation from Maxwell's equation without using the divergence therom (because I haven't read multivariable calc yet!). My physics book gives one but I don't fully ...
0
votes
1answer
51 views

Relative Velocities and Conservation of Kinetic Energy

An object of mass m moves with velocity $v$ towards a stationary object of same mass. Impact is an elastic collision. $v_1$ is the velocity after impact of the mass originally moving $v_2$ is the ...
0
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0answers
25 views

Sum of independent errors [duplicate]

During a physics lab we stumbled upon a little problem. The measuring device was unstable, oscillating between two values. We were told to write down the average with the half-difference between the ...
1
vote
2answers
60 views

Ice throw from industrial wind turbine

I was watching a documentary where the residents didn't want to have a wind turbine erected nearby. One of the comments from the company was that an ice throw would have very little importance since ...
1
vote
1answer
57 views

What volume of helium at standard ambient pressure and temperature is required to lift one kilogram of mass? [closed]

I used the Ideal Gas Law PV = nRT where P is the pressure of the gas P = 1.033 kgf/cm squared V is the unknown volume of the gas n is the amount of substance of ...
0
votes
1answer
69 views

Rigid body problem in 2d

I have some questions about this exercise: In an horizontal plane, a $OA$ bar with mass $m$ and length $a$ moves, with another bar $AB$ (same mass, double length) attached in the point A. In the ...
1
vote
3answers
57 views

Electrostatic and gravitational forces? [closed]

Electrostatic force between two charged particles depends on the magnitude of the charges and the distance between them. If the charges have mass $m$ and $m'$ then, what will be the total force ...
1
vote
1answer
58 views

Normalisation of Linear Harmonic Oscillator - Ladder Operator Method

I was watching the following video on the harmonic oscillator using ladder operators : http://youtu.be/gRdCV9p8sAU?t=30m9s Clicking on the video above will take you to the exact point where my ...
1
vote
1answer
65 views

Calculating the time to stop a wheel with friction [closed]

I'm trying to solve the following problem, but i have no idea how to begin. A wheel of mass $M$, radius of gyration $k$, spins smoothly on a fixed horizontal axle of radius a which passes through ...
0
votes
1answer
67 views

Issue with running a Van De Graaff generator

I am following this online video: http://www.youtube.com/watch?v=fsT69XnjxgU but my Van De Graaff generator is not working. I am using pvc pipes for the body, nylon and electrical tape as two rollers, ...
1
vote
1answer
205 views

Center of mass error - calculating systematic error in change in PE

Suppose we have to calculate systematic error in change in PE. Let's suppose systematic error due to scale is 1%. I'm confused about the center of mass error. \begin{align} \Delta PE = m*g*h_1 - ...