Reaction force on a semi-cubical parabola

[zorro]

Homework Statement

A particle of mass m moves without friction along a semi-cubical parabolic curve given by y²=4ax³ with a constant speed v. The reaction force of the curve on the particle when it is at the point (x = 1, y = 2) is given approximately by

The Attempt at a Solution

F=mv²/r

How do I find out 'r' here?

 

[SteamKing]

I suggest that the r value is the radius of curvature of the path on which the particle travels.

 

[zorro]

I did not ask 'what does r stand for?'!

 

[gneill]

Have you investigated how to find the radius of curvature of a curve? There's a http://en.wikipedia.org/wiki/Radius_of_curvature_%28applications%29" that might shed some light.

 

[zorro]

Oh I see!...so there is a 'ready made' formula for that. Thanks!