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Anderson Video - Mt Whitney Potential Energy

Professor Anderson
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>> So let's say you're taking a hike and you're going to start at sea level and you're going to go all the way to the top of Mount Whitney and let's see if we can figure out how much the change in gravitational potential energy is. Okay, so what do we know? We know that Mount Whitney has a height of 4420 meters. We know that at sea level you are, of course, a height of zero. And so we'll just call this y initial and we'll call this one y final. Okay, what is gravitational potential energy? Gravitational potential energy is the following: u sub g is equal to mg delta y, your change in height. Okay, but we know what delta y is, that's just y final minus y initial. And in this case, y final is h, y initial is zero, so this just becomes mgh. Now if you are hiking this elevation, we need to know your mass, so let's say that you are around 75 kilograms, seems like a reasonable mass. And now let's just plug in some numbers. Okay, so we have 75 kilograms. We have g, which is 9.8 meters per second squared. And then we have h, which we said was 4420 meters. And if you punch all those numbers into your calculator, you should get 3.25 times 10 to the 6th. And what are the units? Well, it's kilogram meters per second squared times another meter, so that's kilogram meters squared per second squared. And if you remember your SI units, that is units of joules. Okay, change of gravitational potential energy is 3.25 times 10 to the 6th. Cheers.