Centripetal accelerations with two parallel axes -- the "Scrambler" 1. The problem statement, all variables and given/known data This should be a pretty quick and straightforward question to answer. The problem regards centripetal forces on an object rotating simultaneously around two parallel axes, like in the "Scrambler" amusement park ride. Basically, one object has uniform circular motion around a minor axis, while this minor axis simultaneously rotates around a major axis (both axes are in the same plane). (Check out the animation at http://www.mrwaynesclass.com/teacher/circular/cd/scrambler/home.html [Broken] and the problems at http://vip.vast.org/Circ_Lab/big_act/index.htm [Broken] ). 2. Relevant equations 3. The attempt at a solution It seems to me you can find the net centripetal acceleration on the rider at point C (where the rider gets closest to the major axis) by finding (1) the centripetal acceleration relative to the major axis and (2) the centripetal acceleration relative to the minor axis, and then (3) subtracting one from the other (since, at C, the two accelerations are in opposite directions). It also seems to make sense that, when (1) calculating the centripetal acceleration relative to the major axis, the radius is given by the distance between C and the major axis, and the velocity is given by the tangential velocity of the major arm (and not by the absolute tangential velocity of the rider) at C -- is that correct? Thanks!!