Notes

Centre of Mass of N-Particles System…

Centre of Mass of N-Particles System –
If there are N-particles distributed in space whose masses are m1, m2, m3,…..mN and position vectors r1, r2, r3,……..rN respectively, then the coordinates of the centre of mass are given below:
XCM = m1x1 + m2x2 + m3x3 + …. mNxN/m1 + m2 + m3 + …. +mN
YCM = m1y1 + m2y2 + m3y3 + …. + mNyN/m1 + m2 + m3 + …. + mN
ZCM = m1z1 + m2z2 + m3z3 + … + mNzN/m1 + m2 + m3 + … +mN
We can also write as,
XCM 1/MΣmixi
YCM = 1/MΣmiyi
ZCM = 1/MΣmizi
where, M = m1 + m2 + m3 + … + mN
The position vector of centre of mass of N-particles system is given by
rCM = m1r1 + m2r2 + m3r3 + ….. + mNrN/m1 + m2 + m3 + … + mN