 Let's do this next problem. It says, what is the combined kinetic energy if you weigh 90 kilograms and are riding 10 meters per second on a 10 kilogram bicycle? So it wants you to find the kinetic energy. So do you guys remember what the formula for kinetic energy is? Because you're going to have to memorize it. So let's do it. So it's kinetic energy equals what? 1 hat. 1 hat. Mass times velocity squared, right? Is that right? I think once you started putting these things in, you would have realized. So let's write down what the problem gives us. So it wants the combined kinetic energy of these things. So it's saying, you weigh, so the mass, we'll say, of the human is 90.0 kilograms. And then the mass of the bicycle is what? 10.0 kilograms. OK, so the mass total is going to be the mass of the human plus the mass of the bicycle, right? Is everybody cool with that? So let's just write it down. So it's going to be the combined, of course, 90 plus 10 is 100, but let's just write it down. Notice the addition of significant figures. So three sig figs, three sig figs, but this has four of them. You can do that with addition and subtraction. So go back to your sig fig rules if you're having trouble. I just wanted to point it out. So velocity, it also gives us, right? What does it say? It's 10 meters per second. It says, we'll say it's 10 dot meters. So now all we do is plug and check. So kinetic energy equals mass, which is 100.0 kilograms times the velocity, which is 10 dot meters divided by one second squared. Divide that whole thing by 2. That's another way of writing my formula. So, here, of course, is 100 times 100. It's 10,000 divided by 2, 5,000. So 5,000 kilograms meters squared per second squared is the unit. But notice this thing's only got two sig figs, right? Everybody see that? Everybody cool with that? Only two sig figs on it? So we've got to have our answer to two sig figs, OK? So it's going to be 5.0 times 10 to the 1, 2, 3 kilograms meters squared per second squared. And what did we say? Kilograms meters squared per second squared was a joule, OK? So the answer is going to be 5.0 times 10 to the joule. Is everybody OK with that? Any questions on it? So I guess when you get to that weird units of kilograms meters squared per second squared, I want you to remember joules, OK?