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Modern Physics

Blazing goIITian

Joined:	2 Jan 2008
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6 Mar 2008 17:01:19 IST

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518

madad karo

None

we know law of conservation of linear momentum

par jab photon electron se takrata hai to vo opposite direction me jump kyo karta hai

is it contradictory to law of conservation of linear momentum

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Comments (7)

aryan smarty pants

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6 Mar 2008 18:22:01 IST

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it is because of unbalanced forces and uncontrolled colissions........

Chirag Sangani

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6 Mar 2008 18:27:13 IST

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conservation of momentum holds in the absence of external forces. You are talking about electron in valence shell of atom. Simple momentum conservation cannot be applied as many forces r concerned...

anand bhanushali

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6 Mar 2008 19:57:27 IST

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are astantine bhai
vo force to collision hone se pehele bhi the
collision hote samay bhi
aur collision hone ke bad bhi

isliye uska is par kese aasar padega

Chirag Sangani

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7 Mar 2008 17:18:59 IST

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exactly! It does not matter whether the forces were there before or after the collision, but it is imp that they be absent during the collision.
REASON-
when external force is zero,
F = dp/dt = 0.
hence total momentum is constant throughout. If force is not zero, then how can u equate initial momentum and final momentum?

anand bhanushali

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12 Mar 2008 14:12:57 IST

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are par kyonki photon bhi ek matter hai
jab vo collide hoga to vo bhi force exert karega na!!!
to force exerted 0 kese????

Chirag Sangani

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12 Mar 2008 15:19:11 IST

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i am taking the system of electron and photon. When there are no EXTERNAL forces, then total linear momentum of this system is conserved, and we can say momentum before and after collision is same. But since there are External forces, momentum is not conserved.
pl. Understand meaning of external force. The force that electron nd photon apply on each other during collision are internal forces.

chemicaltester

Scorching goIITian

Joined: 12 Mar 2008

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3 Apr 2008 21:27:14 IST

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see law of linear momentum is conserved

let me explain u much better (the above post r right)
consider he system before collision of photon
velocity of electrom is v , W and r be radius
a photon is coming with velocity c and mass m
linear momentum at instantenous position during colision are MV and mc
where M is mass of e
now electron engulfs photon to become a exicited one and hence jumps to above level
at this moment
the velocity chenges
but since velocity is proportional to radius
v=wr
it velocity increses
also the mass of electron increses by einstien equation

hence totoal linear momentum conserves

so Mv +mc =M'V'
rate me if u understan
nudge me if there is problem

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