# Reaction force on a semi-cubical parabola

## 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
Staff Emeritus
Homework Helper
I suggest that the r value is the radius of curvature of the path on which the particle travels.

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

gneill
Mentor
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" [Broken] that might shed some light.

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