[tex] \sum_{x=2}^{\infty } \frac{1}{(lnx)^9} [/tex]

[tex] x \geqslant 2 [/tex]

[tex] 0 \leqslant lnx < x [/tex]

[tex] 0 < \frac{1}{x} < \frac{1}{lnx} [/tex]...

Use comparison test to see if series converges]]>

Am i being delusional in thinking ill get acceptwd,? Ive met gead students before and i dont think...

Am i ready for grad school?]]>

Draw a diagram of the orbit and specify its x and y intercepts. Describe its shape.

r = 2bsin(wt)x̂ + bcos(wt)ŷ

Heres my picture. Aren't the intercepts just 2b...

Draw a diagram, specify intercepts]]>

When I connect just the multimeter (as shown in the diagram) to the power source by inserting the lead into the mA connection and change the setting to read the current on the multimeter, it reads 0.

When I change the lead...

Using a multimeter as an ammeter]]>

Mathematics in Physics vs Business/Econs]]>

I have been having problem of the cursor jumping to different place in the middle of typing. It jump to middle of the paragraph and start typing and I have to do ctrl-Z to delete the wrong letters and use the mouse to bring the cursor back. It is happening across a few laptops I have.

I am...

How to prevent cursor from jumping to different places?]]>

A spaceship orbits Earth at 300,000 km distance at speed 0.5c broadcasting live images of the clock aboard, will the clocks difference will be 1 sec?

The orbit is a perfect circle.

Its moving close to the speed of light but stays at the same...

Near-light speed and time]]>

For example: a 2 bit plus a 3 bit binary integer. I would have a 4 bit sum and 3 carries. However, how does one form the appropriate equation...

How does one form an equation for adder/subtractor?]]>

What's your opinion of a Math without Reals?]]>

1. The problem statement, all variables and given/known data

Let V be a vector space, Let ##W_1 , \cdots , W_k## be subspaces of...

Proof regarding direct sum of the dual space of a v-space]]>

1. The problem statement, all variables and given/known data

i was solving the 2008 semi final us physics olympiad paper when i got stuck on question B2 in part 2

http://www.aapt.org/Programs/contests/upload/olympiad_2008_semi-final_soln.pdf

the link takes you a pdf with...

2008 us physics olympiad pendulum in electric field]]>

I need to know what is the best type of susension system for bicycles.And also rating of a motor to drive a 5 kg load.I am still studying B E .Please it is urgent. Thaks for helping.]]>

Ideal Undergrad Preparation for Biophysics Ph.D.]]>

In part a , the author state that at the roller , it will restrain the beam from moving vertically , so the beam wouldnt deflect at roller at part a ... But at b , the author showed that the beam will deflect at roller , why is...

qualitative influence line]]>

Deriving Magnostatics equations from steady currents]]>

Average Coefficient of Kinetic Friction between Ice and Puck]]>

Calculating entropy for a simple scenario]]>

For example,...

using symbolic logic in mathematical proof?]]>

finding intersections in a given range ?]]>

Relation vs. Function]]>

Alternatively, since the gamma radiation penetrates through materials the most, is there a way of "slowing down" the frequency (lowering the...

Decontaminating Radioactive Materials]]>

The object ,lets call it A,Its initally rest relative to us so it can be our inertial referance...

1N Force and going near the speed of light?]]>

Any good lay explanation of the Schrödinger cat duality?]]>

Can a bad reference affect my future?]]>

What sort of camera would you use?]]>

I would like to pose the opposite question: what does the American educational system (K-12)...

What does the American educational system (K-12) teach well?]]>

I have a question regarding to detect the location of the antenna.

I read this link: https://en.wikipedia.org/wiki/Plane_wave

In the "Complex exponential form" part, the equation:

U(r,t) = U0 * exp(j*(k.r - w*t) as the function of location and time

U0 = A0 *...

How to compute the location of the antenna when I rotate it?]]>

I read in Cheng and Li's book "Gauge theory of elementary particle physics" Ch 11, specifically : Eq. (11.46) that the hypercharge commutes with the SU(2) generators, i.e.,

##[Q-T_3,T_i]=0##, I'd like to understand what that mean and how this could be proved ?]]>

I Learned C, Now What?]]>

A cart on an inclined plane is balanced by the weight w. All parts have negligible friction. Find the weight W of the cart using the principle of virtual work. Picture of set-up is attached.

[tex]...

Calculating weights on a slope using virtual work.]]>

The formula for centripetal acceleration (Ac) is $$Ac = \frac {4π^2r} {T^2},$$ where r = radius and T = period of rotation

The above formula can be rearranged as follows: $$Ac = \frac {2π} {T} ×...

Why does the Sin of 0.036 degrees approximately equal 2 pi?]]>

What about the remaining dimensions? Are they there in the regular 3space or are they also encoded?]]>

Same as title.

Taylor expansion.

Okay - what?! I don't even know where to begin. I taylor expanded the function and pretended like n was just some number and...

Taylor expand (1+z)^n where |z | < 1 and n is any complex #]]>

This is the second problem from our test preparation cycle and i partially solved and understood it.

View attachment 111835

Solving a linear circuit #2]]>

View attachment 111886

Say that two charges are held a certain distance apart and are let go. Well, we see that the field lines of one charge repels the other.

And I noticed that the field lines for an accelerating charge also bends....

Do charges accelerate because their field lines are changed?]]>

What form of calculus needs to be used?]]>

Usually, the discoveries on Physics, Engineering, Chemestry and Biology are...

Real advances on CS?]]>

〖 mod note: click on thumbprint image to see legible image 〗

I was wondering if anyone could provide some more insight as to how to find the current through Rc. The first picture...

Transfer function question op amp + voltage divider]]>

As far as I know, mass doesn't exist by itself, it is rather an "attribute" of matter or, let's say it is attached to particles...no particle = no matter = no mass.

Now, inside a black hole,...

The mass of a black hole]]>

A rope of length L is falling off an incline. Part of the rope is still on top of the horizontal surface. There is no friction between the incline and the rope. The incline is at an angle theta above the horizontal.

a) What is...

A rope falling off an inclined plane]]>

If we were to perform the double slit experiment, and shield the detector after a specified time frame to limit the time for a photon to make the...

path integral implies superluminal motion?]]>

For example if we had a block lying between two frictionless surfaces with an angled face ( a slope on one face)...

Linear momentum in oblique collisions and generally]]>

I have a particle associated with a certain spectrum in energy S (differential cross section).

When the particle interacts I use this distribution to have the energy lost.

Now, if my particle interacts 2...

Interaction and probability]]>

I am now considering majoring in physics, but with VT pretty much being my only option for schools (going to UVA...

Virginia Tech Physics?]]>

Here is the last page of part 5.

https://www.physicsforums.com/threads/random-thoughts-part-5.851969/page-134]]>

When they are in space, past 100 km above the surface of earth where there is little air, when it's in the ballistic arc, past apogee does it slow down when it drops or speeds up due to gravitational acceleration without drag? I Am talking...

Question about suborbital flight and ballistic missiles]]>

FeCl

Looking at this database: http://www.knowledgedoor.com/2/elements_handbook/shannon-prewitt_effective_ionic_radius_part_2.html

Knowing that the coordination number of both...

Determining the Ionic Radii of group 2 metal chlorides?]]>

Space station artificial gravity - how to spin up to speed?]]>

Ψ(x,y,z,t)=ψ(x,y,z)e

Show that the probability density is independent of time

Physical chemistry: Energy operator and eigenfunction]]>

So if electrons are fired one at a time, what makes an electron go on a certain path. Say it goes on some weird path that would have implied that a force exist when viewed...

MWI and path of single electron]]>

I already have a basic background so something in more modern stuff would be good. Something along the lines of cosmology or...

Good audiobooks for physics]]>

Hello, I am trying to simplify the inputted function here http://www.wolframalpha.com/input/?i=sqrt(2)+sqrt(1-cos((2pi(x-y))/n))

which is...

Simplifying a trig function]]>

There are some things I think are useful.

- Always research. Don't automatically do something that someone says. Always research it thoroughly. There are almost always others who have had the same questions and often there are...

PC DIY]]>

What causes alternator waveform shape?]]>

Why colonize Mars and not the Moon?]]>

There's a video on the subject here.

On a...

About the SpaceX Interplanetary Transport System]]>

We have found that...

Q re article: Constraints on Dark Matter in the Solar System]]>

In from the cold]]>

please see attached, I am stuck on the second inequality.

attached

I have no idea where the ##2/\pi## has come from, I'm guessing it is a bound on ##sin...

Inequality quick question context cauchy fresnel integral]]>

here at (12:00-12:10) he says.The skater spins respect to space.

My question is How can space-time can be a referance frame itself ?

Is it means we can just pick a coordinate and make...

Can Spacetime be a Reference Frame?]]>

A spaceship traveling close to the speed of light sending some data...]]>

So my problem:

- Stress = tension...

What's the difference between mental and physical stress?]]>

Here is the old archive going back to 03. Holy wow look at my long hair! lol college...

https://www.physicsforums.com/threads/pf-member-photo-thread-archive.7262/

View attachment 111045]]>

It has a flowrate in and out in kg/s. Surely I should look up the enthalpy values and just mutiply with the flow rate to get power in kW.

However I know that if I convert flowrate to m3/s by dividing 1000 and multiplying by the...

Power of a pump]]>

Sonia walks up an escalator which is going up. When she walks at one step per second, it takes her 20 steps to get to the top. If she walks at two steps per second, it takes her 32 steps to get to the top. She never skips over...

Simple Algebra problem, but done with reference frames]]>

I had an inorganic lab this week which involved making VO(acac)

Calculating the number of water molecules in trans. metal complex]]>

Explanation of Biot-Savart Law]]>

the first mistake in this inequality is the...

Problem with CHSH's version of Bell's inequalities]]>

What are other common expressions for "moving a pickoff point" which can be used as" moving a pickoff point behind of a block" or as "moving a pickoff point ahead of block."

Source:Self-made

Thank you.]]>

at the moment I got a bit confused about the notation in some QM textbooks. Some say the operators should be symmetric, some say they should be self-adjoint (or in many cases hermitian what maybe means symmetric or maybe self-adjoint). Which condition do we need for our observables...

Symmetric, self-adjoint operators and the spectral theorem]]>

Thank you for accepting my registration.]]>

I've looked at numerous sources of energy production and have come to the conclusion that instead of...

Whatever happened to geothermal energy production?]]>

0.35 ×...

Why is the DM density near the sun so small?]]>

There's a great video on Youtube showing a...

Evaporating water using heat and reducing vapour pressure]]>

I have a question which is about the lyman break drop-out technique for identifying high red shift galaxies. I am basically trying to understand how the technique works.

My current understanding is that the drop-out technique makes use of the fact that very high red shift galaxies...

Lyman Break drop-out technique]]>

Q1. A pulley 150 mm diameter is driven directly by an electric motor at 250 revs min–1. A V-belt is used to transmit power from this pulley to a second pulley 400 mm diameter against a load of 200 Nm.

The distance between...

Calculating Power/Torque transmitted between 2 pulleys]]>

Find the number of distinct three letter words obtainable from the letters A,B,C,D,E in which E may occur 0, 1 or 2 times but the rest may occur only once.

Number of combinations when picking r...

Permutations with possibly repeating letters]]>

Can anyone advise me how to open this file? Or how to repair dbf?

Any help would be appreciated.]]>

In a two-particle collision the square of the invariant mass is.

M is total mass of the system (M

m is the mass of each particles

E is the energy of each particles

p is momentum...

Two-particle collision]]>

Vacuum Fluctuations in Experimental Practice

...

Vacuum Fluctuations in Experimental Practice - Comments]]>

Building a PC, give me your thoughts]]>

Based on what I know about the status of modern cosmology the question whether the universe is infinite or finite in extent is still open.

Are there any plausible models in which the universe is finite and closed, despite the curvature being close to flat?

Thanks in advance.]]>

Because I was not able to access PhysicsForums recently, I typed everything about my issues into a pdf file that I have attached below.

I am grateful for your help in advance, and make it a great day!

...

Resistor made from two materials]]>

Which of the following is closest to the mean distance between air molecules at room temperature and pressure (298 K and 101325 Pa)? Assume air is made of 79% N2 and 21% O2 by moles.

A 0.4 nm

B 4 nm

C 40 nm

D 400 nm

E 4 μm...

Mean distance between air molecules]]>

I would like some thoughts on the following quote I read from a book on the history of QM:

What 'Collapses' the Wavefunction of the Universe?]]>

Prove that there doesnt exist natural numbers x and y such that the statement holds true.

y^5 + 1 = (x^7-1)/(x-1)

I was able to simplify the term down to

y^5 / x = x^5 + (x^5-1)/(x-1)

Not...

Natural number question]]>

https://www.sciencedaily.com/releases/2017/01/170118163751.htm

Mutations in a gene that should enable memories and a sense of direction instead...

Schizophrenia mice and humans]]>