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18 views

Energy in a string [on hold]

A nylon string of length L = 50 cm and under a tension of T = 70 N is plucked with an amplitude of 5 mm. What is the energy in the string? Please give me the relationship between energy of the ...
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2answers
15 views

Thermodynamic equilibrium- mixing of gases

What is the final temperature and pressure after removing diaphragm of a cylinder which divides the cylinder into two equal components each of volume $0.1\,m^3$ and each component contains air at ...
2
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0answers
23 views

What will be the time taken by a stone to reach the ground if it is thrown with velocity $v$? [on hold]

I was studying from my reference book and I got this question. I tried solving it by finding the total distance n average velocity but it didn't work please help me out.
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0answers
19 views

Finding equation for acceleration using mass1, mass2, gravity, theta, and Mu [on hold]

So, the only question I could not solve in this chapter for AP Physics, and I really want to understand it. We have a situation like this: There is a box sitting on an incline. We are trying to ...
1
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1answer
31 views

Joules To Move A Kilogram In Space [on hold]

If roughly ten joules lifts one kg on earth one meter, how many in space? Meter / joule/kilogram Kilogram/meter/joule
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0answers
32 views

Sturm Liouville Problems [migrated]

I'm currently having a class at university that discusses Sturm Liouville Problems. We have to solve a few problems one of which I can't seem to solve. We use Advanced Engineering Mathematics by Erwin ...
2
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2answers
25 views

Is a given charge density a surface charge density or volume charge density?

The exact question goes like this: In a certain electronic tube, electrons are emitted from a hot plane metal surface, and collected by a plane metal plane parallel to the emitter, at a distance ...
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0answers
22 views

Kinematics/ Projectile Motion Lab [on hold]

This is a question from a projectile motion experiment. Using kinematics you will be asked to calculate the initial velocity of the projectile by measuring its vertical drop h, and the horizontal ...
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1answer
40 views

What causes a spacecraft entering the atmosphere to catch fire? [on hold]

What causes a spacecraft entering the atmosphere to catch fire? A) surface tension of air B) viscosity of air C) high temperature of upper atmosphere D) greater proportion of ...
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0answers
20 views

To find angular speed of a rotating body [duplicate]

A body moving with uniform angular acceleration covers 100 pi (rad)in first 5 s. Its angular speed at the end of 5 s (in rad/s) is?? My ans is 40 pi, but according to the answer given in my book ...
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0answers
16 views

To find angular speed of a rotating object [on hold]

A body moving with uniform angular acceleration covers 100 pi (rad)in first 5 s.its ang speed at the end of 5 s (in rad/s)is??
0
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0answers
24 views

speed of muons relative to Earth [on hold]

A certain muon detector counts 600 muouns / h at an altitude of 1900m and 380 / h at sea level. Given that the muon half-life at rest is 1.5 × ( 10^-6)s, determine the speed of the muons relative to ...
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1answer
48 views

When two objects roll down an incline, does the velocity increase?

I know the basics of rotational motion but this question just confused everything: The answer to the question is A. But why? My problems: If first, I treated both the disks as two particles, ...
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1answer
23 views

Image charge method to find electric field [on hold]

The following is a question from my tutorial on boundary value problems and image charge method- A point charge +q is placed at (0, 0, d) above a grounded infinite conducting plane defined by z = 0. ...
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0answers
32 views

Vectors in three dimensions [on hold]

A plane travels 40 degrees east of north from the Heliport travelling horizontally distance of 2km while reaching an altitude of 2500m and turns travels horizontally another 3km and loosing 1500m in ...
1
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1answer
38 views

Normal modes of two parallel $LC$ oscillators coupled via mutual inductance

Consider the circuit shown below. The two LC circuits are arranged in such a way that their mutual inductance M results in a coupling between the currents flowing in the two circuits. Find the ...
2
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0answers
31 views

Conceptual question on helmholtz equation

Given the homogeneous Helmholtz Equation $[\triangledown ^2 + \kappa^2] E= 0$, I understand $\kappa$ represents the wavenumber $\omega_0 / c$. In light of this, what physical meaning can be taken from ...
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0answers
22 views

Kinematics - Projectile motion down an inclined plane

The inclined plane has angle A over the horizontal. A projectile is thrown down the inclined plane at angle B relative to the incline at velocity V. What is the time taken, range, and max ...
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2answers
40 views

Change of kinetic energy in a two particle collision

A problem I am working on proceeds as follows: A billiard ball of mass $M$ is initially at rest on a horizontal frictionless table. Another ball of mass $m < M$ and velocity $\mathbf{v}$ in ...
1
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1answer
36 views

Uncertainty in position and kinetic energy

How do you find the uncertainties for $x$ and $K$? Knowing that the general uncertainties = $$ \sigma_A \sigma_B \geq 1/2\int \psi ^*[\hat A,\hat B] \psi dx\, $$ I figured out the commutator, for ...
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0answers
18 views

Propagation of Error Formula

I did a lab, and found the Hall voltage for different currents. From these, I was also given the direction, and magnitude of the magnetic field. I need to find the number of charge carriers per ...
0
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1answer
31 views

Temperature Gradient with varying $T$ [on hold]

I'm working on a problem which asks for the temperature gradient at the ends of the rod. The blocks (right and left) are both kept at 0 degrees C. The temperature of the rod is given by $T = ...
1
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0answers
24 views

Moment of Inertia of Polygons in the Plane [on hold]

I was reading this link, which describes a method of finding the moment of inertia of a general convex polygon by splitting it into triangles. I then realized I have no idea on how to derive a such a ...
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0answers
10 views

Partial and total pressure of gases? [on hold]

The problem statement, all given variables and data A gaseous mixture made from 10 g of oxygen and 10 g of methane is placed in a 10 L vessel at 25°C. What is the partial pressure of each gas, ...
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0answers
23 views

Acceleration of Second Leg in One Dimensional Physics? [on hold]

Example: While you are sitting on a park bench with your friend, you grab his hat and start running in a straight line away from him. Over the first $24.2m$, you accelerate at $1.00m/s^2$ up to your ...
0
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1answer
19 views

Projectile velocity and component $x$ and $y$ velocities

So the equations for the X and Y velocity given $\theta$ and $V_0$ are $V_x = V_0\cos\theta$, and $V_y = V_0\sin\theta$. When I test this with something like 1 m/s and and angle of $45^{\circ}$, I ...
0
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0answers
29 views

Determine the eletric potential energy $U(r)$ from a point charge $Q$ at a point $r$ at uniform electrostatic field $E$ [on hold]

I´m trying answer this question but I only have some conceptual ideas. I know that a uniform electrostatic field E is represented by the figure above In my book the author tells that we should use ...
0
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0answers
32 views

Determining Average Velocity [on hold]

I was working on some practice average velocity problems and I came across this one: The position of an object as a function of time is given by $x(t)=(2.0m/s) t - (5.0m/s^2)t^2.$ What is the average ...
0
votes
2answers
26 views

Cylinder falling down the edge of a table [on hold]

Suppose, a cylinder is placed on its lateral side at the edge of a table, carefully, so that the slightest push makes it fall from the table. We give it a gentle push. And it begins to fall. How is ...
2
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0answers
30 views

Proper time integration [on hold]

Say if a clock is lowered very slowly at a speed $v << c$ towards the surface of a spherical mass $M$ of radius $R$ from an initial position $z = R_0$ and returned very slowly at the same speed ...
0
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0answers
16 views

Difference between marginally stable and marginally bound orbits

I have some difficulty understanding what marginally stable and marginally bound orbits are. This is what I have understood: Stable orbits: Stable orbits occur when the 2nd derivative of effective ...
1
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1answer
78 views

Which textbooks contain info on Bessel functions & their use as basis functions?

As an exercise my research mentor assigned me to solve the following set of equations for the constants $a$, $b$, and $c$ at the bottom. The function $f(r)$ should be a basis function for a ...
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0answers
32 views

Conservation of kinetic energy on a moving inertial frame

The velocity of an object differs from the point of views of two different inertial observers standing at two different frame of reference. Assuming no gravity and acceleration = 0 for the object and ...
1
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1answer
20 views

Accelerated wedge [on hold]

Consider the following figure, where a mass $m$ is placed on a wedge which is accelerated to the right ($\vec a$) which could be negative. The coefficient of friction between the mass and the wedge ...
0
votes
1answer
34 views

A problem regarding equivalent resistance between two points [on hold]

I came across this problem in a book which has solutions for all questions except this one. I can't get how to do this partly due my doubt whether the R and 4R resistors will get short-circuited or ...
0
votes
1answer
55 views

Why does the magnetic force exerted by two charged particles on each other do no work?

An electron and a proton are moving under the influence of mutual forces. In calculating the change in the kinetic energy of the system during motion, one ignores the magnetic force of one on another. ...
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0answers
36 views

Show that any rotation can be represented by two successive reflections [on hold]

Show that any rotation can be represented by two successive reflections in two planes, both of which passing through the axis of rotation with the planner angle $\phi/2$ between them
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0answers
31 views

Will there be an induced emf in this situation?

Here is a (horrible) illustration: The first ring has a voltage $V_1$ applied to it through the voltage source on the left. Ring 1 has resistance $R_1$ whereas ring 2 has resistance $R_2$. Will ...
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0answers
17 views

Find the angle and force constituent [on hold]

See picture for the problem description. I know of one way to solve this problem: Use the law of cosines to obtain: $$ 500^2=F^2+750^2-2 \cdot 750 \cdot F \cdot \cos(30°) $$ Rearranging and ...
0
votes
1answer
23 views

Is it only possible when 600J of heat is exhausted and 400J of heat is converted into work? [on hold]

Is it only possible when 600J of heat is exhausted and 400J of heat is converted into work? Is the 600J heat will enter the cold reservoir and available to do work again? q1/T hot + q3 / T cold = 0 ...
1
vote
0answers
36 views

Potential due to a Uniform Ring [on hold]

Consider a uniform ring of mass $M$ and radius $a$ (?). I would like to prove that for $r > a$: $$\Phi(r) = \frac{GM}{r} \sum_0^\infty[P_n(0)]^2 \left(\frac{a}{r}\right)^n $$ Where $\Phi(r)$ is ...
0
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0answers
27 views

Problem in Solving an Equation in Quantum Mechanics [duplicate]

I am trying to reproduce this paper : http://www.ias.ac.in/pramana/v73/p573/fulltext.pdf But, somehow I am stuck at equation (7). The equation that I am trying to solve for particle outside the well ...
-3
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0answers
40 views

Conservation Laws and relativity [on hold]

A 50 kg meteorite moving at 1000 m/s strikes Earth. Assume the velocity is along the line joining Earth's center of mass and the meteor's center of mass. What is the gain in Earth's kinetic energy?
1
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1answer
53 views

Deriving photon propagator

In Peskin & Schroeder's book on page 297 in deriving the photon propagator the authors say that $$\left(-k^2g_{\mu\nu}+(1-\frac{1}{\xi})k_\mu k_\nu\right)D^{\nu\rho}_F(k)=i\delta^\rho_\mu ...
-1
votes
0answers
21 views

Commutator of $SU(2)$ angular momentum operators [on hold]

Prove the following statement. $$[J_i,J_j] = i\hbar\epsilon_{ijk}J_{k}$$ using rotation operators.
0
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1answer
68 views

What are great circles of 2-sphere?

What exactly are great circles, and how does one derive them? Given that the Lagrangian is: $$ L =\frac {1}{2}(\dot\theta^2 + \sin^2\theta\dot\phi^2)$$ it was written that the great circles were ...
0
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1answer
37 views

What is the equivalent resistance of this bridge circuit?

I am trying but could not find any way of calculating the equivalent resistance of this circuit. Please help me. Should I use the Wheatstone Bridge equivalent resistance, the Y-$\Delta$ transform, or ...
2
votes
1answer
31 views

Electrostatic Potential Energy Integral

I'm trying to calculate the total energy of a simple two charge system through the integral for electrostatic energy of a system given in Griffiths' book: $$U = \frac{\epsilon_0}{2}\int_V E^2 dV .$$ ...
0
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0answers
12 views

Deriving (spatial) angular momentum selection rule [on hold]

I am having a go at Problem 7.21 from Binney and Skinner's The Physics of Quantum Mechanics. Here's the first half of the problem: Here is my attempt at the moment: $$[ L^{2}, [L^{2}, x_{i}] = [ ...
0
votes
1answer
19 views

Motion and acceleration in a straight line [on hold]

A car with an initial velocity of 3 m/s has a velocity of 34 m/s after 3 sec. How far it moves in its third second of motion? acceleration V=U + at a = 10.3 m/s^2 x = ut + 1/2 a t^2 x = 3 (3) ...