Flywheels—rapidly rotating disks—are widely used in industry for storing energy. They are spun up slowly when extra energy is available, then decelerate quickly when needed to supply a boost of energy. A 20-cm-diameter rotor made of advanced materials can spin at 100,000 rpm. a. What is the speed of a point on the rim of this rotor?

Video transcript

Welcome back, everyone. We are making observations about a ceramic bearing which we are told spins at 10, revolutions per one minute. And we are tasked with finding what is the speed at a point located at the edge of the 22 centimeter diameter disc. Well, for our velocity, this is gonna be our radius times our angular velocity, but we need to make sure everything is in the correct units here. So here's what I'm going to do. Our desired units is going to be meters per second. So we want to multiply these two things and convert them. So here's how we're gonna do it. Let's first take 22 centimeters and convert it to one m. We know there are 100 centimeters in one m and that cancels out these units and gives us our one m. Remember we are multiplying this by our angular velocity of 10,500 revolutions per one minute. In one minute, there are 60 seconds and in one revolution there is two pi radiant multiplying all of this straight across and canceling out our appropriate units here. What we get is 242 m per second, which corresponds to our final answer choice of d Thank you all so much for watching. I hope this video helped. We will see you all in the next one.