Force of a roller coaster track on a car

[asdf12321asdf]

Homework Statement

The roller coaster car shown below has a mass of 800 kg when fully loaded with passengers.
(a) If the car has a speed of 25.0 m/s at point A, what force does the track exert on the car at that
point. (b) If the car has a speed of 10.0 m/s at point B, what force does the track exert on the car.
(c) What is the maximum speed the car could have at B and still remain on the track?

Homework Equations

F = mv²/r

The Attempt at a Solution

(a)
I thought I would just need to plug into the above formula but that didn't work. I did:
800kg * (25m/s)² / 10m and got the answer 50000N, but that is not the correct answer. I am not sure what else to
Edit: Figured out I had to add in the normal force and got the correct answer.
(b)
Edit: Figured out based on what I learned from part a.
(c)
Edit: Figured out based on what I learned from part a.

 

[PhanthomJay]

Remember Newton's 2nd law...it's not f=ma, but F_net =ma, that is, the sum of all forces(that is, the net force) =ma =mv^2/r. Therb is another force acting on the car besides its weight..the contact force (the normal force) of the track on the car. Solve for it. What is the direction of the centripetal acceleration and the direction of the net force?

 

[asdf12321asdf]

Thanks for the help! I realized I had to also add the normal force when it was at part a. I was able to figure out part b and c based on that information.