JEE Advance - Physics (2009 - Paper 1 Offline - No. 4)
Two small particles of equal masses start moving in opposite directions from a point A in a horizontal circular orbit. Their tangential velocities are $$v$$ and 2$$v$$, respectively, as shown in the figure. 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 the point A?
4
3
2
1
Explanation
The faster particle covers twice the distance covered by the slower one and they meet each other whenever the slower one covers an angular displacement of $$2\pi/3$$. since the masses are same at each collision, they interchange the velocity. The number of meeting points is $$\frac{2\pi}{2\pi/3}=3$$ points; hence, they meet at two points other than A.
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