[填空题]
A roller coaster car with a; me0fr9m nulbb4: bq8 mass of 80 kg moves on the track shown in -k57rty ,yr*n ed ,n)ktvp qp:the diagram start n p7, k)npt:t-kdvr,5*qer yying 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. $v_{max}$ = $ms^{-1}$
