Question

Two charged particles of masses m and 2m are placed distane d apart on a smooth horizontal table. Because of their mutual attraction, they move towards each other and collide. Where will the collision occure with respect to the initial positions?

Answer 1

As the table is smooth, there is no frictioin. The weight of the particles and te normal force balance each other as there is no motion in the vertical dirction. Thus, taking the two particles as constituting the system, the sum o the exterN/Al forces acting on teh system is zero. The forces of attraction betweenthe particles are the interN/Al forces as we have incuded both the partilces in teh system. Therefore, the centre of mass of the system will have no acceleration.
Initially the two particles are placed on teh table and their velocities are zero. The velocityof th centre of mas is therefoer, zero. As time passes, the particles move but the centre of mass will continue to be at the are at one place and the centre of mass will also be at collisio will take place at the centre of mass.
The centre of mass will be at a distance `2d/3` from teh initial positioof the particle of mass m towards the other prticle and the collision will take place there.