In an amusement park, the new roller-coaster ride The Loopy Looper is com- posed of a number of full loops, where the car goes round upside down. The car is attached to the track, but there are no seat belts. Consider one such loop, which can be taken as a circle with radius r. The mass of the roller-coaster car is M, including the weight of the people in it, and you may ignore all sources of friction. The car starts out at ground level with initial speed vi, and after that the engine is turned off. There is gravity g. a) What is the minimum value of vi, for the car to get to the top of the loop, assuming that the passengers hold on to something, to not fall out? My answer: Fs=G m(v^2/r)=mg v^2/r=g v=sqrt(g*r) Am I thinking right?