A planetary gear system can be used as an automobile transmission.  By alternately fixing and
releasing the ring R, the sun S and the arm different transmission ratios may be obtained. 
 If the ring is fixed and  w_Arm =delta.deltadeltadelta rad/sec, find w_Sun . Count the number of teeth to determine the relative size of the gears.

The arm is the triangular plate connecting the pins of the planet gears..