in this video I will talk about the moment of inertia of a mask and a spinning disc so we have to the objects I would have combined the two objects together in a particular fashion how would the moment of inertia would change that's what we're going to calculate so initially we have a uniform disk here a uniform disk and then a mass is placed on the spinning disk or around the disk what would be the the moment of inertia now would it increase or little decrease let's calculate this one so the moment that is so we have given a mum uniform disk with mass is 60 kilogram and radius is 3 meter and it is rotating about an axis passing through its center and now a stone is placed at a distance of 2 meter from the axis of rotation now we need to find out the moment of inertia of the system when I say system that means the stone and the disk together we need to find out the moment of inertia so let's calculate the moment of inertia of the disk so if you have a disk a uniform disk then the moment of inertia is given by dem D which is the mass of the disk already gets a square radius is the radius of the disk here this is power and just plug in the value have the mass of the disk is 60 R square is R is 3 so 3 square this is the moment of inertia of the disk now we'll calculate the moment of inertia of the stone about this axis so this stone can be treated or can be assumed as a point of mass so all the masses here we are in fact it's at the same distance from 2 meter that's the region we assuming this is a point mass okay so the moment of inertia of this stone about this axis is given by M or square here M s stands for the mass of the stone and this part is this distance R so the mass of the stone is 5 this distance is 2 square so 20 so that now the moment of inertia of the combined system would be moment of inertia of the disk plus moment of inertia of the stone together 219 so remember the moment of inertia is a scalar quantity so it is always added together okay and and again all the time we remember you calculating the moment of inertia about the same axis the moment of inertia of this one will be different if the axis of rotation is here so make sure that you calculate the moment of inertia about the same axis and add them together so this is it again if you have any questions write down your questions in the comment section below and do not forget to Like share and subscribe the channel thank you very much