Problem A 60kg woman walking at a speed of 1.0 m/s steps onto a long plank that has a mass of 60kg. Upon stepping on the plank, both she and the plank begin to slide with speed v and spin with angular rate ω on a frictionless surface. 1. How far from the woman is the center of mass of the woman + plank system? a. 0.0m, b. 2.5m, c. 5.0m, d. 7.5m, e. 10m Relevant equations regarding center of mass m1x1 = m2x2, x is center of mass from side of plank where woman is standing The attempt at a solution for woman+plank: [60 kg + (x/10)*60kg] * x & for plank on other side: [60 kg + ((10-x)/10)*60kg] * (10 - x) These 2 equal each other by definition of center of mass We get 60x + 6x2 = 1200 - 120x - 60x + 6x2 60x = 1200 - 180x 240x = 1200 x = 5m This doesn't conceptually seem right to me, but I'm not sure how else to go about this. 5m is the center of the 10m plank, that would be the center of the mass without the woman standing on one end, no? So I'm thinking it wouldn't be with her there? But what is wrong with my calculations if this is true?