TWO SMALL PARTICLES OF EQUAL MASSES START MOVING IN OPP DIRN FROM POINT A IN A HORIZONTAL CIRCULAR ORBIT.THEIR TANGENTIAL VEL ARE V,2V.BETWEEN COLLISIONS,THE PARTICLES MOVE WITH CONSTANT SPEEDS .AFTER MAKING HOW MANY ELASTIC COLLISIONS OTHER THAN THAT AT A THESE TWO PARTICLES WILL AGAIN REACH POIMT A.SIR.PLS EXPLAIN IN DETAIL AND THE CONCEPT U USED.THKSREGDS.

Dear vardaan

collision is perfectly elastic so after colision particle interchange their velocity.

particle having 2V velocity will cover 240 angel between successive colision and particle having V velocity will cover 120 angel between two succecssiive colision

le initially particle having 2V velocity is moving in anticlock wise direction.

angel covered by them is 

θ = 240 -120 +240 -120 +..........=n(360)    {anticlock wise direction is positive and clock wise direction is negative)

it will reach agian at staring point if angel covered by them is multiple of 360

θ = 240 -120 +240 -120 +..........=n(360)

     x*240  -y*120 = n*360

 now put value of x and y suck that it become multiple of 360  here y =x  or y=x-1

 let x=2 ,y=1

  2*240 - 1*120 =360

so total colision is (x+y) =3

if initial colision is not considered then total colision is =2

Please feel free to post as many doubts on our discussion forum as you can.
If you find any question Difficult to understand - post it here and we will get you
the answer and detailed  solution very  quickly.

 We are all IITians and here to help you in your IIT JEE preparation.

All the best.
 
Regards,
Askiitians Experts
Badiuddin