Identify the correct statement. In the absence of external force,a) the kinetic energy associated with the motion of centre of mass is conservedb) centre of mass is not acceleratedc) the centre of mass always moves in curved lined) centre of mass must be at rest

If Fext = Msystem x acmIf Fext = 0, we conclude that acm = 0, so statement (a) is right.Now, K.E. of a system of particles = i.e Sum of K.E. of the particles relative to the centre of mass of the system.Since When Fext = 0, Velocity of centre of mass Vcm is not changing so (b) is right. Hence option - (1) is right.