In the above diagram, sec 1 (on the left side), an object of mass $m$, after releasing from rest from a slant track, continues into a vertical circular track. At a random position on the circular track, I have shown the forces acting on the object. Likewise in the sec 2 (on the right side), an object of mass $m$ climbs the inclined track with a initial velocity $v$. At a random position on the inclined plane, I have shown the forces acting on the object.All of the surfaces have no friction.
Hoping the forces which have shown above are correct, I have below questions:
In sec 1, $N1 - mg\cos(a)$ acts as centripetal force which is required for changing of direction of velocity along the circular track. But what does $mg\sin(a)$ do? Does it acts as the decelerating force which changes the tangential velocity and hence leading this object into a non-uniform circular motion? If so, Is vertical uniform circular motion even possible?
In sec 2, $N2 = mg\cos(a)$ since there is no acceleration in that direction. Also the object decelerates along the inclined plane, with a magnitude of $g\sin(a)$ until $t = v/g\sin(a)$, after that it accelerates back down the inclined plane. Is this analysis correct?
Why are the normal reaction forces are different in the two scenarios? On what does the normal reaction force depend?