There are two disks of uniform density that touch at one point. their masses are in a ratio of 1:9. how many revolutions does the smaller disk make as it makes one rotation around the big circle? (assume that the disks do not slip) This is my try: a is small circle b is big circle M(a)/R^2(a)=M(b)/R^2(b) M(a)R^2(b)=M(b)R^2(a) M(a)R^2(b)=9M(a)R^2(a) R^2(b)=9R^2(a) assume radius of a=1 R^2(b)=9 R(b)=3 Circumference of B 2(pi)(3)=6pi Circumference of A 2(pi)(1)=2pi number of rotations a makes around b 6pi/2pi=3 so three rotations. the answer is four. help.