How can a masseless particle carry momentum and energy?
82353
the classical def of the momentum is indeed p=mv, however, for  massless particles, this def no long applies, for the photon for instance, the momentum is given by\np=h/lambda, where h is the planck constant and lambda, the wave length\nIn that case, energy is given by E=hv, v bieng the frequency of the photon (v=c/lambda)
253742
Please take the time to\nvote for the best answer\n\nThank You!!\n\nRecall that an object of a certain mass moving with particular speed will have an associated kinetic energy  mass x speed2. An object spinning about an axis will also have associated with it a kinetic energy, composed of the kinetic energies of each individual part of the object. These individual contributions may be summed up to give an expression for the total kinetic energy of the spinning object: \n\nLook this up for more
985678
Incoming momentum = p1 = mv1\nOutgoing momentum = p2  = mv2\nChange in momentum = p2 - p1 = m(v2-v1)\nThis change occurs in time, t.\nRate of change of momentum = m(v2-v1)/t = impressed force, f.\nm=0.149 kg, v1 = 43.4 m/s, v2 = -48.7 m/s, t = 1.1x10^-3 sec\n\nf = m(v2-v1)/t\nYou do the arithmetic.
537611
Do you know Einstein's theory e=mc(^2)? In theory (taking out the relevant c for these purposes), it means energy and mass are the same thing ("e" is energy, "m" is mass; a packet of light is considered a particle, etc). Mass and energy are never created or destroyed, simply "change" from one to the other. For example, you get up in the morning and you eat a carrot. I don't know why you'd do that, but say you do; where does that carrot go? G-rated/simply speaking, that mass is translated into energy for your body to use. Your body gives off energy through things like motion and heat when you move, but the mass/concept of the nutrients you received from that carrot weren't lost, were merely translated into an equivalent amount of energy, which your body then gives off. If you go from mass --> energy --> mass, hypothetically, repeatedly, hundreds and hundreds of times, you will end up with the same amount of mass/energy each time.
216275
I believe momentum equals Velocity times Mass.  So momentum is displayed in kgm/s
887139
Momentum is the direct result of the following Newtonian Law of Inertia\nAny object in motion remains in motion and any object at rest remains at rest (unless a net force acts upon the object)\nMomentum (p) is the mass (m) of the object times its velocity (v).\np = mv\n\nForce (F) and Newtons Second Law can be derive from a change in momentum.  That is (t is time)\nF = delta p/delta t \nF = delta (m*v) / dt\nwe usually say m is constant so\nF = m * v/dt\nF =  ma    (a is acceleration or a change in v/time)\n\nNewtons third law is also based on momentum.  "For every action there is an equal, yet opposite, reaction."\n\nSo...  When a gun is fired what we see is the bullet propelled forward and the gun (and gun holder) propelled back.  Both received the same Force but because the gun and person holding it are much more massive than the bullet, the bullet will travel much faster. \ne.g F1 is the force on the bullet which is the same as the force on the person F2\nF1 = F2\ndelta p1/dt = delta p2/dt\nm1v1/dt = m2v2/dt\nm1v1 =m2v2\nImagine the bullet is 1 gram and a 180 lbs (~8182 grams) person shot the bullet...  The avg v on the kick back will be about 1/8182 of the v of the bullet...  Lucky for the shooter.
735972
Conservation of energy and momentum basically means that energy is never created or destroyed, and same with momentum. It has to come with somewhere. If energy or momentum leaves one system, it must enter another system. If energy appears in a system, it had to have come from one. Momentum is never really gained or lost, and same with energy -- it is simply transfered from one body to another. An elastic collision is one in which no kinetic energy is lost, all of it is transfered directly from one system to another.. In an inelastic collision, some of the energy is transfered to a third system (via sound waves, heat energy, or other such energy loss). In this case of an inelastic collision, the total kinetic energy of the two bodies before, is not the same as it is afterwards. The difference in these values would be the energy "lost" from these systems that was tranfered elsewhere.
405474
This is the rest energy of a particle. Energy equals mass times the speed of light in a vacuum squared. This expression became famous for its simplicity, even though it's not really all that practical. I read once that even at absolute zero particles will still have some motion. I'm not sure how one would go about proving that since it's impossible to get anything to a temperature of absolute zero. Anyway since there will always be some movement, the more practical version is:\n\nE = mc^2 /(sqrt(1 - v^2/c^2)), where v is the speed of the particle. (sqrt() is meant to mean the square root of the argument inside the parenthesis)\n\nIt's important to note that this is only true for a particle since you have to consider binding energies if you want to look at anything more complex.
98181
A mechanical wave exists in a medium (which on deformation is capable of producing elastic restoring forces) through which they travel and can transfer energy from one place to another without any of the particles of the medium being displaced permanently; there is no associated mass transport.
945565
Mass. Even photons have a tiny amount of mass due to relativity.\n\nYou were probably thinking of God or Spirits or something else like that, but mass fits your riddle. Do I get ten points?
1122146
A beam of light exhiibits radiation pressure by pushing against any matter it makes contact with.  This shows that the beam of light has momentum and energy.  Einstein reasoned that light energy has the characteristics of mass or inertia.  It has been shown that all forms of energy have inertia and one type of energy can be transformeded into some other energy form.
606680
If by force you are refering to the kinetic energy of a moving object, then the equation is as follows: kinetic energy = one half momentum squared/mass.  Momentum of course can be calculated by mass times velocity.
1129367
so that energy can be transmitted through a medium effectively without having the particles move from one end to the other. they simply need to pass the energy on to the next particle and so on
857646
I found no reference to "inertial motion."  Did you mean inertial mass (m)?  There is also the concept of motion in an inertial frame; perhaps that's what you meant.  [See source.]\n\nAn inertial mass is simply one that fits into the equation F = ma.  (There is also a gravitational mass that fits into W = mg; where W is weight and g is the acceleration due to gravity.  Einstein claims the two masses are equivalent.)  Because F = ma has been proved over and over again, even in high school labs, I think it's safe to say that m does exist.\n\nThe conservation of energy and of momentum laws are two major uses of inertial mass.  These two laws have been proved over and over again; this also validates the concept of inertial mass.
771242
I believe so.  The formula for momentum is mass * velocity.  If your mass is zero or velocity is zero, this will make your kinetic energy zero as well (formula for kinetic energy is 1/2 * Mass * velocity squared).  Momentum and kinetic energy both deal with movement.
29223
electrical weight? um i dont think thats a real term, if you mean an electron has no mass then in fact ot does, its just very small. And to answer your question:\n\nmoving photons have momentum and momentum must be conserved in a collision so the electron would move.\n\nI assume you are talking about the photoelectric effect, which is slightly more complicated as what happens there is that the photons give the electron kinetic energy so they jump out of thier energy level and move freely thus creating a current.
293864
All matter is just a form of condensed energy.\nE=M*C*C, so energy and mater can be interconverted.\n\nRadio/heat/X-ray/microwaves/gamma rays/light  are all forms of electromagnetic energy. It is just a wave, it has no mass, but does have momentum.    Heat and radio waves are light,  your eyes \n\njust can see that wavelength.\nA (infinitely powered)flashlight left on in deep space will eventually begin to accelerate at a measurable pace, due to the momentum of photons expelled from the beam.\nLight has no mass, but does have momentum.\nIf EM light could be bent in such a way, as it would curl back upon itself ( around various phased momentary charges) into a semi-spherical shape, the momentum would trapped into the sphere.  If \n\nyou tried to change the velocity of the sphere, it would push back.  The contained EM momentum now has mass....\n\nSo before the big bang, there must have been an enormous amount of wave energy available.  Photon-Photon interactions don’t generally occur, but can under some extreme conditions.  Once a ( \n\nmomentarily charged)seed Pseudo particle was formed, the seed instantly began to store energy as mass. This quickly lead to the explosion and creation  of a shower of particles including protons ( \n\nhydrogen.  Eventually hydrogen condensed and ignited to form stars/Helium, which ran out of fuel, collapsed and exploded as supernova forging Iron/Calcium etc.\nThe universe has an infinite amount of time, for the unusual set of events to occur, therefore it must occur.\n\n\n\nEnergy can be readily converted into mass.\n\nThis happens in ordinary Endo/exothermic chemical reactions, electrons changing orbits etc. But is so small that the change in mass is difficult to measure.\n\nIt can however, easily be demonstrated in collider experiments, where a small charged particle ( electron for example) is accelerated, and imparted with a energy hundreds of  times its rest mass 511 \n\nk eV.\nAs the accelerated electron approaches the speed of light, its mass increases due to the energy added during its acceleration.  It can become very massive compared to other electrons at rest.  If it \n\nwere to collide with another electron, or high energy photon, this would change its relative speed, ( change in momentum) and convert the huge energy into a shower of particles, including other \n\nelectrons.  In the resulting spray of particles, would be electrons, and other particles adding up to the combined mass of the accelerated particle, and whatever it collided with.  You could very easily \n\nend up with many more electrons than when you started.\nFor each electron produced, you would also find anti-electrons( positrons).  Any charged particle that is formed, in this way always produces its anti-particle, as a particle/antiparticle pair which fly \n\naway in opposite directions, and opposite spins.\n\nOne rule,  conservation of charge. If you add up the charge of all of the particles before, and after, it must be the same.  IF you started with two electrons, then the overall result of the particle spray \n\nshould be -2.\n\nAustin_Semiconductor