﻿[Script Info] Title: [Events] Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text Dialogue: 0,0:00:00.00,0:00:02.00,Default,,0000,0000,0000,,To figure out how many calories you burned, Dialogue: 0,0:00:02.00,0:00:04.00,Default,,0000,0000,0000,,we're going to need to solve for how much work you do Dialogue: 0,0:00:04.00,0:00:07.00,Default,,0000,0000,0000,,and we know from the work energy theorem that the work you do Dialogue: 0,0:00:07.00,0:00:11.00,Default,,0000,0000,0000,,is equal to the change in energy of the weight.and the changed energy of the weight Dialogue: 0,0:00:11.00,0:00:15.00,Default,,0000,0000,0000,,is equal to the change in it's kinetic energy plus the change in it's potential energy. Dialogue: 0,0:00:15.00,0:00:22.00,Default,,0000,0000,0000,,Well the weight starts at rest and it ends at rest too, so the change in kinetic energy is zero. Dialogue: 0,0:00:22.00,0:00:25.00,Default,,0000,0000,0000,,But it does change in potential energy when you raise it at 1 m. Dialogue: 0,0:00:25.00,0:00:28.00,Default,,0000,0000,0000,,Okay, so using energy (mg)h for the potential energy of the weight Dialogue: 0,0:00:28.00,0:00:33.00,Default,,0000,0000,0000,,and plugging in all my numbers, I do a little math and I get that each time I raise the weight, Dialogue: 0,0:00:33.00,0:00:37.00,Default,,0000,0000,0000,,I need to do 100 joules of work but that's just for one raising of the weight. Dialogue: 0,0:00:37.00,0:00:41.00,Default,,0000,0000,0000,,How much work do I have to do to raise it over my 4-minute workout. Dialogue: 0,0:00:41.00,0:00:44.00,Default,,0000,0000,0000,,I chose to do this next part of the problem using conversion factors. Dialogue: 0,0:00:44.00,0:00:48.00,Default,,0000,0000,0000,,The workout takes 4 minutes and there are 60 seconds in 1 minute, Dialogue: 0,0:00:48.00,0:00:54.00,Default,,0000,0000,0000,,so these minutes are cancelled and we do 2/3 repetitions per second, Dialogue: 0,0:00:54.00,0:01:01.00,Default,,0000,0000,0000,,so the seconds are cancelled, and we do 100 joules of work for each repetition, Dialogue: 0,0:01:01.00,0:01:09.00,Default,,0000,0000,0000,,so repetitions are cancelled and there's 1 calorie per 4200 joules, so joules are cancelled. Dialogue: 0,0:01:09.00,0:01:12.00,Default,,0000,0000,0000,,Okay, now let's multiply all these numbers together and we get that Dialogue: 0,0:01:12.00,9:59:59.99,Default,,0000,0000,0000,,over the course of our 4-minute workout, we burned 7.62 calories. Great work.