How Bohr's angular momentum formula derived?

AI Thread Summary
Bohr's angular momentum formula, nh/2π, is primarily a postulate rather than a derivation within the Bohr model of the atom. The discussion highlights the relationship between angular momentum (mvr) and kinetic energy (mv²/2) but emphasizes that the formula itself lacks a derivation. Participants express curiosity about Bohr's motivation for quantizing angular momentum, noting that some of his postulates do not align with modern quantum mechanics. Understanding the intuition behind the formula is acknowledged as a challenge for learners. Overall, the conversation reflects on the foundational aspects of Bohr's model and its implications in physics.
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Homework Statement


Can anyone figure out how Bohr's angular momentum formula nh/2pie is derived? I can't figure it out. I know it has something to do with angular momentum= which is mvr, and Kinetic energy which is mv^2/2. lol, I am stumped.


Homework Equations


angular momentum= which is mvr, and Kinetic energy which is mv^2/2. l


The Attempt at a Solution

 
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Welcome to Physics Forums.
Can anyone figure out how Bohr's angular momentum formula nh/2pie is derived?

Angular momentum =nh/2π is postulated, not derived, in the Bohr model.

http://www.pha.jhu.edu/~rt19/hydro/node2.html
http://www.physics.byu.edu/faculty/christensen//Physics%20106/Graphics/Bohr%20Model%20Postulates.htm

A fair question would be, what was Bohr's motivation for postulating the quantization of angular momentum? That I do not know.
 
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Thanks a lot. That helped a lot. It will take me a while to truly understand the intuition behind the formula. From what I understand, some of Bohr's Postulates do not follow quantum mechanics. I'm still kind of sketchy with the formula, but thanks for your help, it was a big hint.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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