Curvature and Radius of Curvature

Curvature (symbol, $\kappa$) is the mathematical expression of how much a curve actually curved. It is the measure of the average change in direction of the curve per unit of arc. Imagine a particle to move along the circle from point 1 to point 2, the higher the number of $\kappa$, the more quickly the particle changes in direction. This quick change in direction is apparent in smaller circles.
 

Circle of Curvature

 

Vickers hardness: Distance between indentations

Submitted by salveamigos123 on

Hello,
I'm writing here because I don't know how to solve this question that appeared on an exam (undergraduate, mechanical engineering).

The Vickers hardness test was done on a steel plate twice, once with a smaller force and once with a larger force. The first average length of the diagonal is d=0.181 mm. The second indent (larger force was used this time) left the average length of the diagonal d=0.572 mm. What is the minimum distance between indentations?