Reference Definition and 1000 Threads

Sorry for the lame question, but I was wondering if someone could help answer the following. I have two synchronised clocks which I place on two different space ships which then accelerate away from me at the same rate and time until they reach a given speed. Ship A then slows down to be at...

Dear PF Forum, Sorry if I ask again, because I want a detailed information. Does the universe has a frame of reference? Two twins. A stays, B "travels". (Travel here is confusing, B will say I stay and A travels) and B "turns around" and come back. B ages more slowly then A. Q1: Why? A1...

Little bit of a disclaimer: if you take a look at my first (introductory) post, you'll see that I'm working towards aerospace engineering; therefore, this is leaning towards turbopump design, but for the time being I'll start out slow. Basically, I'd like it if anyone could help me get a sense...

Hi Friends , I had a discussion with a funny person last night. He said the following argument : Suppose there are 21 objects including the one object under consideration. Each of the 21 objects move with a velocity. Since there are 21 objects, for the object we are considering has 21...

Dear PF Forum, Again the same question about preferred frame of reference. I have read several threads in Physics forum, but I think this question belong to cosmology. And I have searched in Google and in PF forum threads, so, I'll ask some confirmation here. 1. Does the universe have a...

When I was surfing on a group in Facebook, I found two concepts very difficult to understand by reading the discussions in comments. Those concepts are inertial and non inertial frame of reference. Please make me understand these two concepts in simple words. Please don't suggest links as I...

Homework Statement I am reviewing for my midterm and I just want to quickly understand a concept. It seems that velocity does not depend on the original reference frame. For example, let's say spider man is standing on the ground next to a 78.4 meter tall building, and it is known that if he...

Homework Statement A wheel of a bicycle weighs 1 kg, all of which is at the rim. The diameter of the wheel is 0.7 m. If the bicycle is ridden at the speed of 3.5 m s–1, then in the frame of reference of the rider: i) Calculate the angular speed ω of the wheel. ii) Calculate the momentum of...

Homework Statement Our teacher said we can NEVER do an F=ma problem from an accelerating, or noninertial frame. (He said there are ways to do it, but we can not do it in his class), and I'm confused becuase often times he makes the "system" or makes a "free-body diagram" around an accelerating...

Who is the trigger of the oxidation reaction. Copper which attracts electrons from the Zinc or solution which makes Zinc losing electrons and become positively charged. I am struggling to understand what actually makes Zinc to enter the solution and leave 2 electrons behind. If there is no wire...

I'm working a contract job and was offered a salaried job at the company but turned it down after holding on to the offer until they put pressure on me to make a decision. I think they knew that I was holding on to it as a backup plan while trying to get an offer somewhere else. Well, I pretty...

Hi All Physics newbie here... Just a quick question regarding Inertial and Non-Inertial Reference Frames. From what I understand: Inertial = One that obeys Newton's Law of Inertia. Moves at constant velocity in one direction Non-Inertial: One that accelerates. Right? So, I read somewhere that...

Hi, I am new here, but there is a question that really bugs me :-(. In Lorentz force why was the velocity defined as relative to the observer and not relative to thesystem generating the magnetic field. By defining it relativ eto the system relativity is not needed to explain how an observer...

I had a though last night that kept me awake trying to figure out what I was trying to understand. I have been out of school many years now so I have forgotten much.. Here is my question. Lets imagine there is a 30 meter diameter hole (complete with a vacuum) in my front yard that goes through...

Homework Statement An inclined plane, fixed to the inside of an elevator, makes a ## 32 ^\circ ## degree angle with the floor. A mass m slides on the plane without friction. What is its acceleration relative to the plane if the elevator accelerates upward at 0.50 g? Homework Equations...

what is the best referece book to study atomic structure and electronic structure of atoms ?

Hi Folks, I have some misunderstanding how one can add velocities of different coordinate systems. Consider a planet gear rotating about its own axis and also rotating on its carrier so that the so called velocity of the planet gear relative to the carrier is the planet local velocity minus...

Homework Statement Hello! I would be grateful for your help. I've tried many many times to record a mixed reference macro on my mac, and it doesn't record a thing. No problems with recording separate macros with relative or absolute reference. Problems description: I have few sheets with...

At about 05.30, Dr. Lewin makes a small calculation to find the centripetal acceleration one experiences due to Earth's spin (at the equator). He then says that because of how small the magnitude of this acceleration is, we could consider the Earth's surface to be an inertial reference frame...

I've decided to work on some topics about supersymmetry for my undergraduate thesis. My background is that I have had a one-semester course in differentiable manifolds, plus typical undergrad math courses, real analysis and module theory (graduate algebra). So, I went to the library and found a...

Hello, I have a question regarding the concept of torque and reference frames. Say for example I have a rod of length L and that the rod has it's right side anchored to act as a pivot point. Now let's say that I input a force on the left side of the bar in an upward direction. Assuming that...

I'm studying special relativity for the second time and there's something I think I didn't get since I studied classical mechanics: the idea of a frame of reference. I think the underlying idea is that of a point of view, so that we want to study some phenomenon, but we have to observe it so...

While trying to understand how each frame of reference predict that the other is slower, I discovered what seems to be something unsymmetric. It looks as if it is possible to determine that a frame of reference is not one truly standing still. But that's impossible right? I'm really interested...

So I understand that in classical physics, movement only makes sense with reference to another body. So my car moves relative to the surface of the road, for example. But it seems that with acceleration, things appear to be more complicated than that. Let's say we have two objects in space...

An accelerating charge radiates light. But in its own frame of reference it is stationary. So it does not emit light. How is this explained? Extreme Example: A charge inside an elevator is falling in a gravitational field. The elevator is lined with a light sensitive sensor that triggers a...

Homework Statement A uniform plank of length L = 6.0 m and mass M = 90 kg rests on sawhorses separated by D = 1.5m and equidistant from the center of the plank. Cousin Throckmorton wants to stand on the right-hand end of the plank. If the plank is to remain at rest, how massive can Throckmorton...

The question is A long metal cylinder with radius a is supported on an insulating stand on the axis of a long, hollow, metal tube with radius b. The positive charge per unit length on the inner cylinder is λ, and there is an equal negative charge per unit length on the outer cylinder...

I'm a STEM major, college sophomore, looking for an internship this summer and a place I'm applying to needs 3 references, after I finished my interviewed there. I tried contacting my manager from my intern position last year asking if she'd be a reference. Problem is she didn't respond after a...

I'm reviewing physics after ~30yrs of neglect, starting with Halliday & Resnick (and the internet). Here's what I understand to be standard Newtonian/classical inertial frames: 1. There exists a set of reference frames, called inertial frames, in which mass, time, force, acceleration, etc. are...

You are standing on one. The two planets were closing in on a speed of 1x. You just accelerated one of the 2 planets towards the other with a super powerful rocket engine, and then sat on one of them. Now they are closing in on each other at speed 10x. The universe is otherwhise empty. The...

I'm still very early on in my reading, so forgive me if this question isn't coherent. In the "historical introduction" section of the 1920 University of Calcutta translation of the original papers of Einstein and Minkowski available via the MIT online archive, mention is made of the fact that...

Dear experts, I need to study wave motion in detail. Mainly mechanical waves on a string, reflection of mechanical waves, standing waves, resonance etc. I am looking for a book which covers these basic concepts in minute detail. For example , I believe that the phase shifts during wave...

Hi, I am looking for a good reference book for "Fredholm integral equations". + a book with lots of examples related to this topic! Thanks for your help.

What is the definition of an inertial frame ? I've read that Inertial frames are reference frames in which Newton's first law applies (i.e.bodies subject to zero net external force moves at constant velocity) , however Newton's 1st law itself is only valid under inertial frames. I find it weird...

I am looking for an introductory reference to the subjects 'Probability and Statistics' intended to be used for self study.By an introductory reference I mean an undergraduate level text that would teach me the subjects from the very basic to an advanced level.I wish to focus primarily on...

Hello, I have a few questions about rotation and relative motion. Suppose we transport the proverbial spinning ice skater used to demonstrate conservation of angular momentum to beginning physics students to a universe with only her and two planets. She is now spinning in deep space...

I am working on a lot of things with electric motors, and many other electromechanical devices. Any textbook comes to mind?

Homework Statement Let S and S' be two inertial frames of reference where S' is moving at a velocity of 0.6c relative to S. When x = x' = 0, t = t' = 0, where t and t' are time of the clocks on S and S' respectively and x and x' are the x-coordinates of the S and S' frames respectively. An...

If you have a car and a pendulum is hanged inside it, and if you watch from outside the car,and if the car has some acceleration, then you see the bob moving in opposite direction of motion of car. For a person standing outside, he knows that the car has some acceleration. What causes the bob...

I need a reference book to read the following topics- a) Generalized coordinates; b) D'Alembert's principle and Lagrange's equations; c)Hamilton equations; d) Motion of rigid bodies in two dimensions. The topics need to be covered only at graduation level. Thanking you in anticipation.

Alright so I'm still trying to get a hang of the theories of relativity, and this thing has really been bugging me. All forms of motion (and sometimes even physical observations) are defined for a particular local frame of reference. But is there any "stationary" frame of reference in the...

Hello, I was wondering about a question and how it would be reconciled within Newton's laws of motion. Take a case where two boxes are stacked on top of each other, and the bottom box rests on a frictionless surface. Now, imagine a rope is attached to the top box, and tension is applied to...

I have a 3-pack of related relativity musings I was hoping someone(s) could enlighten me on: 1) Since the reach of gravity is infinite and the universe is homogeneous and isotropic with regards to the distribution of matter, is it fair to say that no object, even those in deep interstellar or...

Reduction half reaction : Cu2++2e- -> Cu(s) I have a doubt in using the reference electrode. For example if I have the calomel electrode (ESCE=0.24V) how do I use it with the copper half cell? Are these reactions correct? Cu2++2e- -> Cu(s) 2Hg+2Cl -> Hg2Cl2+2e- To get Ecell=0.24+ECu|Cu2+

Would it be acceptable to look at post-doc offers (as a pre-PhD student) and email the offerer to ask whether they would accept a PhD in X field? If a post-doc says it requires you to have a PhD in a "closely related field", would it be alright to email them and ask if you do a PhD in something...

My apologies for the numerous times this has probably been posted, but I wasn't able to find a great answer through the search tool alone. Please correct me on anything I state incorrectly, and direct me to the answer.. My question is, if the speed of light is 299,792,458 m/s, its speed is...

Last Tuesday ,I came across an old lady[looking a bit disorientated] in the street who asked me "Is today a Sunday ,I need to go to church?" I said to her "Its a Tuesday" This set me thinking about "phases of the moon","364.25 days for Earth to orbit Sun", 52 weeks made up of 7 days etc etc...

I've managed to get through all of this question without trouble until part d). The full question is given here: I've calculated the "true" angles of Star A and Star B as 71.57 degrees and 45 degrees respectively in Frame S, and the "light" angles should be the same, since the stars are...

I am currently working on a circuit design that is featuring both a ADC and DAC. I'll focus my question on the ADC in this thread. I'm trying to figure out what each pin does. Am I correct in assuming that the Vref pin on the an ADC chip is used as the maximum encoded value for a voltage? Say...

Homework Statement A water spider maintains an average position on the surface of a stream by darting upstream (against the current), then drifting downstream (with the current) to its original position. The current in the stream is 0.408 m/s relative to the shore, and the water spider darts...