Hello. I have what I hope to be a simple question. It's something that I've come across in several problems in my engineering and physics subjects and I'm not sure exactly what relationship applies. My text book doesn't seem to be very helpful in the matter. When there are two circles, I suppose you could call them gears, of different sizes with a belt wrapped around them, what is the relationship between their velocity? I'm talking about both their angular and tangential velocities. I know that in a rotating disc the angular velocity will be the same at each point on the disk but the tangetial velocity will change as you change your radius from the centre of the disk. I have a feeling that either the tangential or angular velocity will be the same for these two disks attached by the belt with 1 of them being turned by a motor and, in turn, turning the other. This isn't a homework problem but I've attached a simple example diagram with simple numbers to illustrate my question. Here it is the smaller disk being turned by the motor at a given angular velocity and I'd like to know what I can therefore infer about the larger disk. Thank you kindly in advance for your help, David.