Q.An isolated particle of mass 'm' is moving in a horizontal plane (X-Y) along the X-axis at a certain height above the ground.It suddenly explodes into two fragments of masses m/4 and 3m/4. An instant later,the smaller fragment is at y=15 cm.The larger fragment at this instant is at ?

Dear Raj

As the particle is exploded only due to its internal energy. So net external force during this process is 0. So the centre mass will not change.
Let the particle while explosion was above the origin of the co-ordinate system. i e just before explosion X=0 and Y=0

Centre of mass will be at X=0 and Y=0

after explosion Centre of mass will be at X=0 and Y=0

Ycm= [(m/4 * 15) + (3m/4 * y)]/m =0

solving y=-5cm

All the best.

AKASH GOYAL

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