good afternoon and welcome to tale physics and today I am going to talk about work and power now the formula for work is one of the most powerful formula that you'll be using throughout the course so it's really important that you come to grips and understand every formula for energy you will come across will be can be related back to this work formula and work the formula for work or the letter W is Force Times distance now this this is very similar to the moments formula however the moments formula is the distance from the pivot to the force and it makes a perpendicular is that the distance and the force must be perpendicular to each other this is the distance in the direction of the force so if an object is being pushed this way with ten Newton's over a distance of two meters the amount of work that must be done to do that must be 10 times 2 which is 20 joules of work so here I'm doing 20 joules of work to move from here to here in the same direction as this now work is a scalar quantity okay even though we do talk about it's in the direction of it is a scalar quantity so it doesn't need a plus or a minus next to it and just to show you how important this woman it is if I start talking about the work done by dropping this object the force that's causing that is of course the weight so for a dropping object the force is weight which is mg and the distance is traveling is the height and that there miss GPE gravitational potential energy I'll go look at another one I'm gonna have an object that is accelerating okay so I'm gonna have an object with a force on it that is M a times by the distance okay and I'm gonna have here the average velocity so I want the I want to look at the acceleration at the average acceleration so I'm gonna need the average velocity for that so that is going to be M times V over to C so it's the average velocity divided by the time which is the exert that that would be acceleration times white distance and of course this here distance divided by time is another velocity so ends up with M times 1/2 times V times V I ends up with 1/2 MV squared which is also known as kinetic energy you can replace this force with any known force formula that you are using Coulomb's law gravitational field strength gravitational our soda Newton's law of gravitation that force equation the Coulomb's law one you'll be able to produce numerous results about energy now it's really important this is in the direction of the force so if your object here has a force of 10 Newtons this way and you want to know how much energy to move it 10 meters and this is 60 degrees you need to work out how it energy you need to move it this 2 meters so you need to find the component here in the direction of the force this is the hypotenuse that is the adjacent so I'm going to use cos so cos 60 equals FX over 10 10 cos 60 equals F X which is 5 Newton's so the energy that I'm using to go this direction would be 5 times 2 which is 10 so that is work and it's one of the most important energy for the knee in the whole course which brings me on to power power is the rate of work so it's how quickly you are exerting that work power this is a big pain not to be mixed up at pressure or momentum is work over time when you see the word rate that does mean dividing by time power is measured in what or Big W so if it takes me two seconds to move this object with 10 Newton's for 2 meters I would have my work is 20 divided by 2 so that's 10 watts of power now this formula here this work done can be replaced by any any energy formula she can use MC delta T for specific heat capacity you could use ml you could use mg hey she could use harvest bird this energy this work thunk can we replace for energy any energy formula and this is because all energy formulas come from this formula here work done and that is work done and power [Music]