And then what did that energy turn into? If this was the initial position, what kind of energy do we have when the mass gets right above That's it, we just had gravitational potential energy to start. We won't have that for this example, because there aren't any springs, so there won't be any And this US here is gonnaīe any spring energy. So if we drop this mass, it starts with no kinetic energy. Was there any kinetic energy? No, because it was released from rest. Say there were four units of gravitational potentialĮnergy to start with. No matter what you draw over here, you just wanna be consistent when you then draw this diagram over here, and I'll show you what The real value in this LOL diagram is being able toĬonceptualize what's happening to the energies. Weren't like three, or five, 'or 4.2?' Well, it doesn't really matter too much. You know there were four? 'How do you know there So I'm gonna say there were four units of gravitational potential energy. So I'm gonna represent that with this bar. So what kind of energy was there initially in this system? There was gravitational potential energy, because this mass M startedĪt height H above the earth. So now that we've selected our system, we can go ahead and starting charting what the energies look like. Mexico, and South America, and there's Florida, and then there's all kinds of stuff here. It's got continents, and it's got California, and The energy of this mass, and then if you're talking about gravitational potential energy, here's the weird thing, you're also talking about the earth. 'That's gonna be part of my system.' So I'm gonna take this mass here, and I'm gonna make that part of my system. What you're really doing is you're saying, 'I'm taking my mass. With potential energy, and then it turns into kinetic energy. The way people typically do this problem when they're doing conservation of energy, they would say it starts Part of our energy system, whose energies are we gonna keep track of, and whose are we not gonna keep track of. The first thing we should do is choose what is gonna be Let's say you took a mass M, and you released it from These LOL diagrams mean, let's just look at an actually example. Gonna define our system, and then another chart. This is an energy chart, a circle where we're And notice, it looks like an L, and then an O, and then an L. Or a collection of objects whose energies were gonna keep track of, and we're gonna keep track What an energy system is, maybe that's where we should start. Visualize conservation of energy, and even better, theyįorce you to think about what's part of your energy system and what isn't part of your energy system. You pick the reference point based on what objects are relevant to the question. So the velocity you care about is the relative velocity between the ball and the sun.

compared to if the ball were sitting stationary on the sun), the ball would have kinetic E of the Earth's movement as well. But if you zoomed out and considered the ball's kinetic E with respect to the sun (i.e. So the velocity you care about is the relative velocity between the ball and the floor. (This is usually implied rather than stated explicitly)Īnother example: When a moving ball 'has kinetic E', it's usually meant in relation to if it were stationary on the floor. You have to be comparing 2 states the object is in. But it could have potential E relative to it being on the ground. So when the ball is on the table, you'd say it has 0 gravitational potential E relative to it being on the table surface.

It's always relative between 2 different states of the object in question. The important thing to recognize here is that 'energy' is not an absolute amount.

Draw me physics