Circular motion object falling in the circle

[Khunpol Jermsiri]

Homework Statement

An object with mass of m traveling in a circle rail ,when reached point A the object derailed and moved in a parabola path to point B and so on find the length of AB in term of R and theta. given that B is on the same horizontal level as A

Homework Equations

The Attempt at a Solution

i don't get the idea .if its stop moving in circular that mean there must be no centipetal force which mean the velocity must be 0 or there must be another force with the same quantity as centipetal force.(the picture is upside down btw sorry!)

 

[kuruman]

The object is moving in a parabolic trajectory as shown in your figure. There is a radius of curvature to the trajectory which means that there is a centripetal force directed towards the center of the (instantaneous) circle that the object describes. This centripetal force is supplied by the appropriate component of gravity.

 

[LEDan]

Great answer Kuruman, that homework question takes me back!

 

[CWatters]

i don't get the idea .if its stop moving in circular that mean there must be no centipetal force...

No that's not correct.

The magnitude of the centripetal force required to move in a circle of radius r is given by mv^2/r. If the net centripetal force is greater than that value the object will move in a tighter circle (eg smaller r).