IIT JEE , AIEEE Forum - Physics , Electricity

malay

nikhil
I have something for you.

first notation, since I can't use usual notations due to inability

a: mass of electron
b:mass of proton
e:charge of proton
r:the required distance
v:initial velocity of electron
w:final velocity of proton

the question is one dimensional interaction between proton and electron. The system consists of electeon and proton, and they attract each other through conservative electric field(magnetic effects are neglected).

Applying law of consevation of momentum
av=a*2v-b*w
(if electron is moving initiallly in positive x-direction, then finally it will be moving in +x and proton in -x due to mutual attraction)

Aplplying law of conservation of energy
a*v*v/2=a*2v*2v/2+b*w*w/2-eV(r)

Using, these two equations, you can find r

if you find w from first equation and substitute in second equation, you observe that kinetic energy of proton involves square of a/b, which is very small and hence can be neglected.

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