Answer: 77.5 m/s
Explanation: We can use the following equation to calculate the velocity of the roller coaster car:
velocity = sqrt( (normal force + weight) * radius / mass)
where weight is the gravitational force acting on the car (mass * g)
Substituting the given values:
velocity = sqrt( (-12,000 N + (600 kg * 9.8 m/s^2)) * 6 m / 600 kg) = sqrt( -12,000 N + 5,880 N) * 6 m/s = sqrt( -6,120 N) * 6 m/s = 77.5 m/s (round to the nearest tenth)
The negative sign on the normal force indicates that it is acting in the opposite direction of the gravitational force. This can happen when the roller coaster car is upside down, which is the case in this problem