quest---two particles of mass1kg n 3kg move towards eachother under their mutual forceof attraction. no other forceacts on dem.tjheir rel...velocityof approach is 2m/s. find vel.ofcentr of mass/.well mjhe quest galat lag rahatha......wat u thnk.......since itsans is nt given.. so m ntconfirm

Well I also think that it is incomplete

The initial conditions are not given 

Are they at rest?

If yes then 

The v of COM remains unchanged = 0

Dear Hemant

Question is correct

suppose particles(m and 3m) are placed at some distance r. take origin at m

position of centre of mass= m*0+3m*r/4m = 3r/4 from m

now if they start moving then from action reaction force on both will be same but due to mass difference acceleration will not be same. if acc of m is a then acc of 3m will be a/3. so there will be relative acceleration they will move towards each other with relative acc of 4a/3 and the value of a will not be constant. as gravitational force is proportioal to 1/r² hence a is also proportional to 1/r². centre of mass will also change its position as both move with diff acc and diff velocity.

so please confirm the question that is the force constant or v=2m/s is at what instant.

All the best.                                                           

AKASH GOYAL

AskiitiansExpert-IIT Delhi

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Dear student,

Here concept of reduced mass wll be used..

Mr=m1m1/m1+m2

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Sagar Singh

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