## Essential University Physics: Volume 1 (3rd Edition)

We know that we have to balance the forces along the radial direction $N+mgcos(\phi)=\frac{mv^2}{r}$ When the contact is lost then the normal force becomes zero, that is $N=0$ $mgcos(\phi)=\frac{mv^2}{r}$ $cos{\phi}=\frac{v^2}{rg}$