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### Energy=pc

Posted: Thu Oct 18, 2018 2:56 pm
KE=1/2 mv^2, but why is Energy=pc true instead of Energy=1/2 pc?

### Re: Energy=pc

Posted: Thu Oct 18, 2018 5:51 pm
You can't treat these equations equally, in other words you cant just add an exponent or multiply by one half. If you tried to equate 1/2mv^2 it would look like 1/2pc^2. I see what you're saying because p=mv. However, in the first equation you're squaring velocity, but not squaring mass. You can't square the variable p on the other side because p includes both mass and velocity, you also can't square c because c is a constant, so it wouldn't make sense to. The same thing applies for the 1/2, although it seems logical because p=mv and mv is used in the first equation, because of the difference in values in velocity(v versus v^2) and the addition of the constant, you can't just add the 1/2.

### Re: Energy=pc

Posted: Fri Oct 19, 2018 12:26 am
KE= 1/2 mv^2, it is only velocity squared, not m. energy would not equal 1/2 pc, as p=mv. It isn't (mv)^2.

### Re: Energy=pc

Posted: Fri Oct 19, 2018 3:03 am
In the equation for kinetic energy, mass is not squared. Only velocity is.

### Re: Energy=pc

Posted: Fri Oct 19, 2018 10:05 am
I'm confused, when is mass squared in 1/2 pc? Isn't that for electrons, 1/2 pc=1/2 mv*c=1/2 mv*v?