[填空题]
A roller coaster carjdn ive0*+ 4vav lbid;+4z2do:qqg22d ivvs*k j0;qhwith a mass of 80 kg moves on the track shown in the diagram starting: qv22*h qsvjikg;0dq from point A.
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. $v_{max}$ = $ms^{-1}$
