X-coordinate of CM is at origin
hence,0=(2m(−a)+4m×a+m×a+m4(−a)2m+4m+m+m4)
or0=3ma−m4a
∴m4=3m
Four particles of masses m1=2m, m2=4m, m3=m and m4 respectively are placed at the four corners of a square. What should be the value of mass m4 so that the centre of mass of the system of particles lies at the centre of square?