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**1. Homework Statement**

Two balls with masses m1 and m2 moving on a horizontal table in the same direction but at

different speeds collide elastically.

Obtain expressions for the position and motion of the centre of mass in terms of the

separate positions and motions of the two balls before they collide. Take it that at the

instant of observation they are passing x = x1, x2 respectively with speeds v1 and v2.

How would your expressions simplify if m2 >> m1, while v1 and v2 are not very different.

If m2 >> m1 and v2 << v1, what happens in the collision?

**2. Homework Equations**

Xcm= M1X1 + M2X2/M1+ M2

**3. The Attempt at a Solution**

Well, for separate positions the cerntre of mass should be same as above equation. But what about just before the collision?