Massless Definition and 285 Threads

Homework Statement A pion spontaneously decays into a muon and an antineutrino according to pion^1- => muon^1- +antineutrino.. Current experimental evidence indicates that the mass m of the antineutrino is no greater than about 190 keV and may , in fact, be zero. Assuming that the pion decays...

help me! Homework Statement Three blocks on a frictionless surface are connected by massless strings, with M1 = 1.80 kg, M2 = 2.80 kg, and M3 = 3.70 kg. Due to the force F acting on M3, as shown, the system accelerates to the right. Given that T1 is 2.70 N, calculate T2 Homework...

Forgive if I'm being sarcastic, but I just read on the Higgs mechanism, giving mass to the fermions and bosons. But at the same time, Higgs itself has mass? Isn't that abit irony?

how can an elementary particle like a photon be massless? How can physicist measure and detect a photon if the don't know its inherent properties? I know a photon travels at the speed of light , but wouldn't you have to know a particle mass , in order to know its speed? Or are physicists...

I read that fermions really should be massless when you write down the Lagrangian, as it violates the gauge symmetry. It's the Higgs coupled to them that give them their masses. I was so shocked. I have only learned QED and abit of QCD Lagrangian, and the fermions did have masses in the...

Light is known a as some kind of energy that is being radiated; and energy is known as the fundamental source for any work. In addition, energy is known to be massless and so is light. Also light is the result of proton particles traveling in a very high speed known as the speed of light, which...

I know this isn't a deep discussion and the thread will be short but this question has been bothering me for a while and I hope the moderators won't terminate it. Are photons the only massless particles that travel at the speed of light? Diagrams of the standard model do not reveal the...

I know photons have no mass but are there other particles that have no mass and if so can they travel at the speed of light? Thanks RAD

Homework Statement A massless spring hangs from the ceiling with a small object attached to its lower end. The object is initially held at rest in a position yi such that the spring is at its rest length. The object is then released from yi and oscillates up and down, with its lowest...

Hi, I am new to the forum. lol. I came here because in my physics class, many of the experiments call for massless string. Does anyone know where I could purchase some? I understand it is harder to come by, but I am willing to pay extra. Thanks a bunch

(I hope I've chosen the right sub-forum for this question...) Hi folks - I've recently joined here to see if people who are more knowledgeable than me can help me understand some physics issues I have struggled with for a long time. My current question is a pretty basic one about how it is...

do massless particles not feel forces - other than gravity? The only massless particles I know are photons and neutrinos. Photons feel gravity, but other than that, once a photon is created, is its energy fixed? Laura

I've been doing some reading on QCD, and I keep running into the notion of "massless quarks". Are they massless in the sense that if you look at E = \pm \sqrt{p^2 + m^2} the p^2 term dominates and E \sim p or is this something completely different?

I'm not sure this is the right forum, but I wanted to ask the following (possibly bizarre) question: Is it implicitly assumed that zero rest mass particles have momentum in the same direction as they travel?

I recall my teacher explaining this concept in class, but he did not go over how we would solve these types of problems: Bob the monkey (20 kg) is on a small platform (2 kg), which is attached by massless rods (R = 3m) to a frictionless pivot, and initially at rest...

Two masses (mA = 3 kg, mB = 6 kg) are attached to a (massless) meter stick, at the 0 and 75 cm marks, respectively. a. Now, if mass B was removed, how much force would need to be exerted at the 100 cm mark in order to keep the meter stick level? b. Now, if mass B was removed, and no...

A 3 kg mass and a 4 kg mass are attached to either end of a 3 m long massless rod. If the system is rotated about the center of mass by a force of 7 N acting on the 4 kg mass, (perpendicular to the rod), what will the size of the angular acceleration of the system be? I used angular...

Hey all! New to the forums here, and I must say, I've been greatly enjoying all the reading. Just three quick questions to ask... If one were able to have the 'perspective' or viewpoint of light, then they would see time as non-existent correct? They could go anywhere whenever and time...

In modify minimal subtract sheme,using dimension regulation, I calculate the the renormalization constant of massive quark and massless quark,get the same result.But in some papers,they are different. Is there a review or any book on MS renormalization,that giving all the self energy and...

I've been studying the Yang-Mills theory, which predicted the existence of massless charged particles. That theory was later proven to be wrong, but it made me wonder nevertheless - can there ever be massless charged particles? And if such particle exists, how will it behave? How will it...

It was my understanding (however my understandings are wrong 99.9% of the time) that a electron was massless, and that it took the form of a wave that collapsed into a specfic point when it was "located" however, I was told that I am my friends AP physics class, there are told to use the...

A uniform sphere of mass m and radius r is held in place by a massless rope attached to a frictionless wall a distance L above the Centre of the sphere. Find the tension in the rope and the force on the sphere from the wall. I tried to get a picture, but it is apparently too big to host...

Electrons are "massless"? Why are electrons described as "massless". It seems to me that they would have to have mass. Are they truly massless or is this the same kind of aproximation that is made with ideal gas laws?

"Massless" electrons behave relativistically This is just one of a zoo of examples from condensed matter where relativistic forms manifest themselves via condensed matter phenomena. http://physicsweb.org/articles/news/9/11/6/1 Just imagine. One could have a benchtop demo of QCD! Zz.

Given: A massless particle revolving in a circle with a rotational velocity = (2+sin(a)) To Find: Y-axis acceleration Method #1 (from rotational acceleration) Y-axis acceleration = (2+sin(a))(cos(a))^2 Method #2 (from Y-axis velocity) Y-axis acceleration =...

A mass m is attached to a massless rod of length L to make a pendulum. In addition, when the rod is vertical, two relaxed springs with constants k1 and k2 are attached on either side of the mass to walls. What is the period of oscillation. I started by writing the potential energy as a...

For the tunnel-effect, the relation between the transmissioncoefficent T and length of the barriere L is: T=e^{-2KL} in which: K=\sqrt{\frac{2m(U_0-E)}{\frac{h}{2\pi}^2}} Now, the tunnel-effect is possible for light right? But light means m=0, meaning K=0, meaningT=1! I must be...

Alright I'm having a little trouble on this one... One end of a massless spring is welded to a flat surface; the other end points upward. A mass of 2.0kg is set on top of the spring. The spring is then compressed by hand so that the end of the spring is 42cm lower than the position of the...

how is it that some strings have mass (spin 1/2 particles) while others have no mass at all (spin 2 particles and force carrying particles)? all strings are the same, its just how they move and vibrate that they change from particle to particle, but wouldn't this mean that all strings either...

I'm sure this is a very newbie-level question, but how is it that massless particles and light are affected by gravity? I've been reading about the 'ghost condensate' theory, and the latest article in New Scientist that says these massless 'ghost' particles should have been sucked up by black...

Does light is massless ?

I've heard that it is thought that Neurinos are massless paricles, but I'm now hearing that they have kinetic energy. Can something with no mass have kinetic energy?

"Massless" Particle? What is meant by a massless particle? I know that a photon is massless and travels at the speed of light. Then how is it that a black hole ( or gravity) can affect it? I thought that gravity affects only objects with mass.

A massless, frictionless pulley is suspended from a rigid rod. Two masses, m (50 kg) and M (60 kg), are suspended on either side of the pulley, respectively, by a light, inextendable cord. Determine the accelerations of the masses. I drew the force diagrams of both; there is an upward...

So I have a wave incident on a boundary problem. The incidence is normal and the boundary is a knot of mass 'm' at z = 0, with the wave coming from minus infinity. The problem is that the string on the other side is massless, and I can't figure out exactly how that effects the boundary...