in this video I will talk about how to calculate they work done by friction or we're doing the work done against the friction so let's get into that we have an object and a force is applied and there's a friction force as well this object is moving with a constant speed it could be 2 meter per second it could be 5 meter per second as long as it is a constant speed and now we have to find out how much work is done by the applied force if we move this object 5 meter let me drink it the question one more time so we'd have an object that is a 50 kilogram object and we applying a force and the object is moving with 5 meter per second let's say so how much work is done if we move or if the distance moved is 5 meter so we're going to calculate this one now as the object is moving with a constant speed that which the total force is exactly equal to zero an object can move with a constant speed only if the total force is exactly equal to the zero and as we have we're applying applied force then in order to make the total force zero there must be a friction force there must be some opposing force and this opposing force or the friction force must be equal to the applied force only then the object will move with a constant speed or in other words as the object is moving with a constant speed this force and the friction force must be exactly equal so let me demonstrate this one using a simulation just give me one second just taking a little bit time okay so we have a using the fate simulation here so now let's say you have this mass here which is a 50 kilogram mass and I'm applying a lot of friction here and now let's see and now here I'm just changing the the force what you can see here the total force is exactly equal to the zero and the M and the friction force and the friction force and the and the applied force is exactly equal that with the total force is zero and the object is not moving and now now the when the applied force is now greater than the friction force the object starts moving okay so but when the two forces were exactly equal the object can either be at rest or it is moving with a constant speed so now let's calculate the amount of work done so we have given the mass is fifty kilo gram the coefficient of a static the coefficient of kinetic friction is point four that is this is between the block and the ground so as I already mentioned the friction force is exactly equal to the applied force so we let's calculate how let's calculate the friction force the friction force if you have to calculate the friction force you need to know what is the normal force you have to calculate the normal force this is the formula for calculating the friction force the K stands for the kinetic friction force which is equal to MU it is pronounced as mu mu and n is the normal force and in this case if you look at the free body diagram the object is not moving anywhere so the normal force in the vertical direction so that this normal force must be equal to the mg M is a exactly equal to mg so that we know mu and now M n this n is equal to M times G which is mu is equal to M Stan G so we know the MU value which is the copy center kinetic friction I can write down here is mu K which is 0.4 and the N the mass is a 50 kilo gram and the expression due to gravity G value is 9.8 so we know now the frictional force which is 196th Newton and as our object is moving with a constant speed the friction force and the applied force must be exactly equal which is 196 Newton so the work done now the work done as you know that the force times the displacement and Here I am NOT using the cosine component or cosine theta because the force and the displacement are in the same direction so the force is 196 Newton and the displacement is 5 Newton which U which is given a 5 meter and if you multiply them together you will get 980 Joule so this is the amount of work done or walk down against the friction that's exactly the same thing here ok so again if you have any questions write down your questions in the comment section below and do not forget to like share & subscribe the channel thank you very much