|Class 11 Physics Rotational Motion||Motion of COM|
Motion of COM
out each other)
We can obtain the translational component of their motion, i.e. the motion COM of the system, by taking the mass of the whole system to be concentrated at the COM and all the external forces on the system to be acting at the centre of mass.
Example - A child sits stationary at one end of a long trolley moving uniformly with a speed V on a smooth horizontal floor. If the child gets up and runs about on the trolley in any manner, what is the speed of the CM of the (trolley + child) system?
Solution – In this case if we take (trolley + child) as a system, there is no external force involved.
The force involved in running of child (friction) becomes internal, so the speed of CM of this system remains constant.