Applies to questions of primarily educational value - not only questions that arise from actual homework assignments, but any question where it is preferable to guide the asker to the answer rather than giving it away outright. Please READ THE GUIDANCE IN META before asking homework-like questions.

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2
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1answer
25 views

Work in gravitational field

I was doing a test a few days ago and there was a fairly simple task involving gravity basics. The task asks me to calculate the work done by moving an Earth's artificial satellite from a stationary ...
0
votes
0answers
22 views

Relativistic Lorentz Force with constant, perpendiuclar, and uniform E and B fields

I am trying to solve the following problem from the Fundamentals of Plasma Physics by Bittencourt (Problem 2.7): Analyze the motion of a relativistic charged particle in the presence of crossed ...
0
votes
0answers
12 views

A force in a homogeneous magnetic field

Semi infinite parallel conductors, while on them without friction slides a crossbar . Perpendicular the plane of the conductors is a homogeneous magnetic field. To what extent of force we must act on ...
0
votes
1answer
43 views

Why can this question about Centripetal Force not be answered in this way?

Here is the question: "A car travels round a bend which has radius $100 m$ and is banked at an angle of $20°$ to the horizontal. The car is travelling at a speed of $30 ms^{-1}$. What is the least ...
-1
votes
1answer
15 views

Period of a spring in SHM (simple harmonic motion)

An object with unknown mass M is hanged on a vertical spring with unknown spring constant K, the spring is in rest and is 14 cm from its normal point (if it didn't had the mass hanged it had less 14 ...
-1
votes
1answer
12 views

combination of mirror and lens

a convex lens forms a real image of a point object at a distance of 50 cm from convex lens. a concave lens is placed 10 cm behind convex lens on image side. on placing a plane mirror on the image side ...
0
votes
1answer
11 views

Condition for sliding of two blocks placed one over another and connected by spring

A constant force F is applied to smaller mass till M slides. The spring constant is k. Now it is asked to find k. I'm confused with the condition at which the block will start sliding. Can ...
0
votes
1answer
42 views

Where does this relativistic relation involving the delta function come from?

\begin{equation} \int\delta(E^2-\mathbf{p}^2-m^2)dE=\frac{1}{2E_\mathbf{p}} \end{equation} Shouldn't integrating the delta function like this just give 1?
0
votes
0answers
19 views

physics numerical on vectors [on hold]

Question:- The sum of the magnitudes of two forces acting at a point is 18 N and the magnitude of their resultant is 12 N. if the resultant makes an angle of 90° with the force of smaller ...
0
votes
1answer
18 views

Total potential energy for two charged particles

I'm trying to formulate a Lagrangian equation for a system of two charged particles. They have respective masses $m_1$ and $m_2$, and respective position vectors $\vec{x_1}(t)$ and $\vec{x_2}(t)$. ...
0
votes
0answers
24 views

Question about Gauss' law and dipoles

I've got a question about dipoles and Gauss' law: Consider an electric dipole $p=ql$ in free space, centred at the origin of a Cartesian reference frame. Using Gauss’s Law, discuss if the electric ...
0
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0answers
19 views

Work done by a gas in an expansion

1) Consider a gas expanding quasistatically and reversibly from $V_1$ to $V_2$ at constant temperature. I want to calculate the work done. So by convention work done by a system is a negative quantity ...
1
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0answers
20 views

How to find the generators of a deformed boost?

I'm reading the paper arXiv:gr-qc/0012051 on doubly special relativity. In page 7, the author wants to find the generators of a deformed boost that preserves $$E^2 = p^2 + m^2 - l_p p^2 E$$ ($l_p$ is ...
0
votes
0answers
8 views

Path of puck through a turntable

I was looking a problem which tells me to consider myself standing on the ground beside a perfectly flat horizontal turntable rotating with constant angular velocity w. Then I lean over and shove a ...
-4
votes
0answers
19 views

Kinematics Question - Motion in two dimensions [on hold]

Suppose there is a 11. 7 ft wide ditch with the approach roads at an single of 15 degree with the horizontal. If the length of bike is 5 ft and it leaves the road when the front part runs out of the ...
-2
votes
0answers
11 views

Heat energy question [on hold]

An aluminium block of mass 1 kg is heated by an electric heater for 3 minutes and a temperature rise of 15 °C is recorded. If the electric heater is connected to a voltmeter which gives a reading of ...
0
votes
1answer
20 views

An example on computing the density of a typical nucleus

An example from my text is as such: Compute the density of a typical nucleus, and find the resultant mass if we could manufacture a nucleus with a radius of 1cm. I will only provide a partial ...
0
votes
0answers
39 views

Why they put rocks in Railway tracks? [on hold]

Why they put rocks in Railway tracks? Each time i see there are many rocks are there in railway tracks, but what is the purpose of putting rocks?
0
votes
2answers
36 views

Static friction and Kinetic friction

I can't seem to find this anywhere on the internet or on stack... Sadly. Very basic question: I have a block that is on a surface. The coefficient of static friction between the two is $0.3$, ...
-2
votes
0answers
17 views

What is the speed of the charge in this setup of spherical conductors? [on hold]

Two concentric spherical conductors respectively have radius $r_1 = 0.145\ \mathrm{m}$ and $r_2 = 0.207\ \mathrm{m}$. The inner sphere carries a charge of $-6.00 \cdot 10^{-8}\ \mathrm{C}$ . An ...
-2
votes
0answers
19 views

Classifying solutions of equation of state as functions of temperature

I've got an exam in 2 days and the past papers don't have solutions. I'm given this equation of state: $$ p + a\frac{N}{V} = \frac{Nk_BT}{V-bN}$$ and asked to classify the solutions as functions of ...
1
vote
0answers
23 views

Semi infinite parallel conductors [on hold]

Semi infinite parallel conductors separated by a distance of 0.5 m are at the endpoints associated with the resistance R = 4, while according to the two without friction slides bar by weight: 0.1 kg ...
-3
votes
0answers
25 views

In the solar system are located planet A and B [on hold]

in The solar system are located planet A and B. A and B are their heliocentric distances distance. A is planet on the outer = 1 a: e: and bypass -Time PA = 365 days. Assuming coplanar orbits. A ...
0
votes
0answers
22 views

Find the equivalent capacitance

On the plane capacitor below, the surface of the boards is $A$ and the distance between the boards is $d$, the dieletrics constants are $k_1$ and $k_2$. Find the capacitance of the capacitor in ...
0
votes
0answers
33 views

One extra conservation equation or angle relation for a relativistic collision

Edit: It seems that the derivation for the center of momentum frame was incorrect, due to the fact that the center of momentum velocity changes after the collision. This is also true for the ...
-4
votes
2answers
31 views

Find the total current supplied to the circuit [on hold]

I tried but could not manage to find the correct equivalent resistance. Please tell the process. The answer is 3A
0
votes
0answers
10 views

Expression for the heat capacity of an ideal Bose gas

I've been desperately looking to solve this problem through various mathematical tricks but it seems that there's something that I'm missing here. Consider an ideal Bose gas. If one notes the ...
1
vote
0answers
23 views

Find the time needed to warm the water to a temperature [on hold]

An electrical resistence has a power of 1 kW. It is put inside a container that has 10 liters water. The water is in temperature 20C with pressure 1 atm. Find the time to warm the water to the ...
0
votes
0answers
17 views

Find the molar specific heat for each gas [on hold]

A mixture of two ideal gases, the first one atomic and the second two atomic are put in normal conditions in a calorimeter with volume 1 liter hermetically closed. After it is given 10J thermal energy ...
1
vote
1answer
33 views

Find the velocity of the escape of the bullet

A gun has a muzzle 0.8 meters long and with a diameter of 0.006 m. A bullet with mass 0.002 kg is initially 0.01 m away from the end of the muzzle. As a result of a gunshot, the pressure of the gas ...
-1
votes
0answers
41 views

Electric field outside a sphere

The sphere $K\subseteq R^3$ with radius $R$ has a homogeneous charge density $\rho$. Find the electric field E, produced by K outside of, meaning, find the integral ...
0
votes
2answers
83 views

What does this equation mean?

So I have just entered 11th grade and started limits on my own but my Physics textbook has an equation which I don't understand, I suspect it uses integration which I haven't learned yet. So can ...
0
votes
1answer
14 views

What is the fraction of the incident intensity passing through polarized sheets?

Unpolarized light is incident on a set of three polarizing sheets as shown in the figure at right. The polarizing directions of the sheets make angles 10°, 55° and 85° to the vertical. What fraction ...
0
votes
0answers
19 views

Would any interference maxima be missing in the double slit experiment? [on hold]

An aperture of 0.9mm of double slit forms a diffraction pattern on a screen placed 6.0 meters away when illuminated with light of wavelength 600 nm; the distance between two slits are not specified. ...
0
votes
0answers
20 views

Amplitude of electric field produced by satellite dish [on hold]

A telecommunications satellite is in geostationary orbit and it has a 1 m transmitting dish optimised for coverage of Europe. If the output power from this dish is 100 W, very roughly estimate the ...
-1
votes
0answers
13 views

Relation of current with frequency and voltage [on hold]

I tried to solve a numerical problem but I got stuck and I think it very necessary I will drwa certain basic conclusions when I would found its solution. The question is: An incandescent lamp ...
0
votes
1answer
15 views

Derivation of impedance matching formula

When matching impedances with a quarter wavelength coupler, how do I derive that its impedance has to be $$ Z_2=\sqrt{Z_1 Z_3} $$ where $Z_1,Z_3$ are the impedances of the adjacent materials?
-1
votes
0answers
10 views

Calculating work needed to move a charge between plates of an uncharged capacitor [on hold]

My first guess was zero work because there's no electric field(I think). E.g. a parallel-plate capacitor $4.9 cm$ on a side, spaced $1.0mm$. The work needed to move $6.8\mu C$ seems to be $1.1J$ And ...
-2
votes
2answers
39 views

Finding the initial velocity of projectile [on hold]

What is the formula for calculating initial velocity of projectile using the conservation of energy given the mass, height, angle ?
0
votes
1answer
38 views

Are $Q1$ and $Q2$ attracted or repelled to the sphere shown in the figure below? [on hold]

Can you tell from the image below if Q1 and Q2 are attracted or repelled. Will Q2 only be attracted to the sphere if Q2 is enough bigger than Q1? Will the positive charge inside the shell attract ...
0
votes
0answers
17 views

Find direction and magnitude of net electrostatic force on a point charge

Question: Find the direction and magnitude of the net electrostatic force exerted on the point charge $q_2$. Let $q = +2.4μC$ and $d = 33cm$. What I tried: I used the formula $F = kq_1q_2/d^2$ to ...
1
vote
2answers
76 views

Conservation of angular momentum - exercise [on hold]

A sphere of mass $M$ is rotating with constant $w_0$ regarding the axis that intersects the north and south pole of the sphere. A bug of mass $m$ sits on the north pole and starts to walk along a ...
-3
votes
0answers
25 views

Resistors in series [on hold]

Let $P$ be the equivalent power of three resistors of powers $P1$, $P2$, and $P3$, and let $I$ be the current flowing through the circuit. We know that voltage is $V = v1 +v2 + v3$ and: $$V = PI\\ ...
-3
votes
1answer
28 views

Non zero accetion, varying speed

Can an object have non zero acceleration without having varying speed? How? Can you explain with an example please.?
-2
votes
0answers
21 views

Max speed of a turning disk for an object to stay at rest [on hold]

A coin is at rest relative to a disk moving with a angular speed of w: The coin weighs 0.010 kg The distance of the coin to the center of the disk is of 0.20 m The static friction is of 0.45N ...
-1
votes
0answers
21 views

Finding the magnetic field [on hold]

A mechanical pendulum is made of a metal rod, one end of which is attached to a string. The mass of the rod is $m$ and the string length is $l$. The oscillation period of the thus obtained pendulum ...
0
votes
0answers
17 views

Initial current, RC Circuit

The task goes like this: The voltage between the points A and B, in the circuit diagram below, is 100 V. What's the initial current through the resistor when we close the switch S? (Other components - ...
-2
votes
0answers
21 views

Finding displacement of spring [on hold]

Q) A block lies on a horizontal frictionless surface, and the spring constant is $50\,\mathrm{N/m}$. Initially, the spring is at its relaxed length and the block is stationary at position $x=0$. ...
0
votes
0answers
23 views

The minimum force required to lift a triangular prism

If I have an isosceles triangular prism of mass m with the angle at the top being $2\theta$ I want to work out the minimum force I would need to apply to the upper faces to lift the prism. Lets say ...
0
votes
1answer
51 views

Solving the Three-body problem numerically

I want to create a program in $Mathematica$ that solves numerically the Three-body problem by Euler-Lagrange's equations. I was searching some methods to sucessfully do it. So I found a way to solve ...