Quick physics question

[Bobsessed]

what is the formula for calculating the momentum of an object?

i fully forgot..

is it P=mv?

or did i just imagine that?

[insane_alien]

yep you got it.

[swansont]

Unless it's a photon, in which case it's p=E/c

[ydoaPs]

Unless it's a photon, in which case it's p=E/c

 

Or [math]\rho=\frac{\hbar}{\lambda}[/math]

[Klaynos]

Or [math]\rho=\frac{\hbar}{\lambda}[/math]

 

surely p not rho?

[swansont]

And h, rather than h-bar

[5614]

Well ya got the divide by lambda bit right!

[Bobsessed]

Thanks.

I dont understand anything past the first comment. But ok.

[5614]

Basically: p=mv is correct, for all "normal" cases.

 

But when dealing with particles, or more specifically a light particle (aka a photon), which has no mass, you cannot say p=mv, becuase m=0. So instead a different formula, [math]p = \tfrac{h}{\lambda}[/math], is used. Where h is Planck's constant (just some number) and lambda is the wavelength of the light (or photon - same thing).

[Royston]

Deleted, due to brain fart