Rest, velocity is zero, so kinetic energy becomes zero. This time what's the final kinetic energy? Well, the tempo is at The final kinetic energy minus the initial kinetic energy. So from work energy theorem we say work done equals How much kinetic energy got added to this tempo. Thing what we did before, we can say work done is Work done on the tempo, again we are given the mass of the tempo, the mass is given to be 500 kilograms. So that means this time itĭecelerates, so after a while it comes to a stop that means Is initially traveling, initially traveling atģ0 meters per second. All right lets see, a 500 kilogram tempo, travelingĪt 30 meters per second, brakes and comes to a stop. A pretty similar problem so great idea to pause and see if youĬan try yourself first. Velocities are given, we can accurately use work energy theorem to calculate the work done. Joules of kinetic energy and so that must be the So this equation is basically saying that the car gained, sorry, the truck. So let's put everything in one frame now. How much is that equal to? That is 500,000 Joules. Truck should equal final, which is 900,000. So we can do that now, so work done on this Now work done just representsįinal minus initial meaning how much kinetic energy got added. So this is the initial kinetic energy, this is the final kinetic energy. Okay, so if we simplify we get again, goes one times, so 1000 kilograms into 20 square is 400. And again if we substitute and simplify, lets go down a littleīit to make some space. Similarly, the initial kinetic energy will be half into M, into Of energy, isn't it? We also call this as joules, so we'll just call it as 900,000 Joules. Five zeroes, right? Kilogram meters square per second square. So we get 1000 kilograms times 900 meters square per second square. We get a thousand here and 30 square is 900. So we can now plug in the values and if we simplify we will get Two goes one times, so Kinetic energy of our car? That's going to be half M into And to recall, kineticĮnergy is half MV squared. So get ready to pause the video and see if you can try this yourself. Anyways, now by calculating how much the final kinetic energy is and how much the initial kinetic energy is, we can now calculate what the work done is. It would be a great idea to go back and watch that video and And if you need moreĬlarity on this equation we have talked a lot about this equation in a previous video called And that itself represents the work done. So I just have to calculate how much kinetic energy wasĪdded when the car accelerated. So in this example, if we find out that 10,000 joules of kinetic energy was added to this body, then it means that the workĭone was 10,000 joules. And the equation is basically saying that the work done onĪ body basically tells how much kinetic energy And this equation canīe derived from here. So work done equals final kinetic energy minus the initial kinetic energy. Which says that work done equals change in kinetic energy. What do we do? Well, maybe we can use this data and calculate what forceĪnd displacement is and then substitute and calculate, right? But guess what, we'veĪlready done this before! If we were to plug in for F equals MA and somehow substitute all of this, we will eventually arriveĪt an equation called the Work Energy Theorem We are only given the initial and the final velocities and the mass. Do I know what the displacement is? That's also not given. Okay, now do I know what the force is? No, that's not given in the problem. So, how do we calculate work? Well, we have seen now for quite a while, work done is calculatedĪs force acting on a body multiplied by theĭisplacement of that body. Truck, that's given to be, let's just write that down How much is the work done on this truck, given its mass is 2,000 kilograms. It goes a little faster so now it is at 30 meters per second. Going at 20 meters per second, let's write that down. Truck before accelerating, so before it accelerates it's We are given that the truckĪccelerates from 20 to 30, so let's say here is our Okay, let's go ahead andĭraw a situation for this. Find the work done on the truck, given its mass is 2,000 kilograms. Here's the first example: A truck accelerates fromĢ0 meters per second to 30 meters per second. Solve a couple of problems on calculating work when
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