The discussion revolves around calculating the kinetic energy of a particle in a relativistic dynamics context. The original poster presents a scenario where a particle of mass m with kinetic energy K collides with a stationary particle of mass 2m, resulting in a composite particle of mass √17 m. The challenge lies in finding the value of K using conservation laws.
Participants are actively engaging with the problem, asking for clarification on the original poster's attempts and suggesting ways to manipulate the equations. There is a recognition of differing views on the concept of rest mass versus relativistic mass, indicating a broader discussion on terminology and its implications in the problem.
There is mention of the original poster's struggle with recurring issues in similar problems, suggesting a potential gap in understanding the application of relativistic concepts. Additionally, the discussion touches on the evolving terminology in modern physics regarding mass.
Hi Rudy. Not necessarily.rude man said:Does the composite particle have zero K.E.?
You should be able to manipulate and combine the momentum balance and the energy balance into a single quadratic equation involving the variable x = K/(mc2). It takes some playing with the math to bring this about. So, as Strange said, show us what you did, and maybe we can give you some hints on manipulating the math.Scientist94 said:Homework Statement
A particle of mass m and kinetic energy K strikes and combines with a stationary particle of mass 2m, producing a single composite particle of mass √17 m. Find the value of K
Homework Equations
E= γmc^2 , p = λmv
The Attempt at a Solution
I have tried many times at this and have used the conservation of energy and conservation of momentum but I seem to get nowhere. The equations are definitely solvable and this seems to just be algebraic manipulation. My question is whether there is any way to simplify these problems as I just cannot get an expression for K without the other variables, this problem keeps cropping up in other questions too!
Chestermiller said:Hi Rudy. Not necessarily.
Chet
What's wrong with invoking rest mass? That seems to be a large part of what this problem is about.rude man said:Hi Chet, right. Hadn't realized.
I'll leave this one to you, assuming the OP responds. Lately the only responses I get are from other helpers ... bedides, I'd only invoke rest mass again, stirring that controversy up again probably.
rudy
Chestermiller said:What's wrong with invoking rest mass? That seems to be a large part of what this problem is about.
Chet
Yes, I see. There used to be rest mass and relativistic mass. Now, for good reason, there's no meaningful quantity called relativistic mass. Rest mass and m are now one and the same.rude man said:I learned 'modern physics' in the early '60's when there was a separate symbol for rest mass: m0. Recently it was pointed out to me in these forums that that is no longer in vogue: there is only one mass, m. If at rest it's m, if moving it's γm. So among other casualties it's no longer E = mc2 but γmc2, and p = mv is no longer correct either. I find this change entirely pointless but found out to my distress that I was in the rank minority ... I suppose I made a mountain out of a molehill but still I see no reason to fix what isn't broke.