[填空题]
A roller coaster car with a mass of 80 kg movd(xqg6 m, osu+j3sermb65od, es on the track shown in the diagrao xjm,sg (5m3 drub+s66o qde,s0wgg/. w s.gem starting from point A.s/. gwsegg 0w.
At points B and C, the track approximates a circular path so that the radii at at B and C are $12,m$ and $18\,m$ respectively.
1.Compare the normal force exerted by the track on the car at point B is the corresponding force at point C.
2.Draw and label the free body diagram of the car at point C.
3.Calculate the maximum speed of the car at point C so that it could remain on the track. $v_{max}$ = $ms^{-1}$
