Circular Motion Force at Point A: Stunt Car on Frictionless Track

[Help1212]

Homework Statement

In the figure, a stunt car driver negotiates the frictionless track shown in such a way that the car is barely on the track at the top of the loop. The radius of the track is 9.9 m and the mass of the car is 1800 kg. Find the force of the car on the track when the car is at point A

http://session.masteringphysics.com/problemAsset/1107086/1/7.10.jpg"

Homework Equations

Accelaration(radius) V²/R F=ma

The Attempt at a Solution

massxacceleration =1800kg x V²/9.9m ... v²=1800kg/9.9 =181 .. v=13.4 m/s

F=1800kg x (13.4)²/9.9

Can someone help me please.. what am I doing wrong?

 

[WatermelonPig]

Is the loop vertical? Is the car traveling on an inclined slope?

 

[Help1212]

sorry for the confusion i included a picture link for the problm

 

[gneill]

If the track is frictionless then his trajectory is ballistic; he can't use the engine to accelerate because the tires have no friction with the track.

The condition posed is that the car is "barely on the track at the top of the loop". So work out its required speed there. Then use whatever conservation laws spring to mind.