A roller-coaster car has a mass of 500 kg when fully loaded with passengers. (a) If the vehicle has a speed of 20.0 m/s at point A, what is the force exerted by the track on the car at this point? (b) What is the maximum speed the vehicle can have at point B and still remain on the track? Is the answer to (b) dependent on the tangential acceleration? For part (a), I found the force exerted on the car by the track to be m( g - ( v^2 ) / R1 ) = 500( 9.8 - ( 20.0 / 10.0 ) ) = 3900 N. Then for part (b), I have 0 = mg( ( vmax^2 ) / ( R2 * g ) - cos 0 ) -> vmax = ( g * R2 )^( 1 / 2 ) = ( 9.8 * 15 )^( 1 / 2 ) = 12.1 m/s. Am I in the ball-park?