If you want to pile up sand onto a circular area of radius R, the greatest height of the pile to be erected without spilling sand on to the surrounding area is ($\mu$ - coefficient of friction between sand particles) - Clay6.com, a Free resource for your JEE, AIPMT and Board Exam preparation

If you want to pile up sand onto a circular area of radius R, the greatest height of the pile to be erected without spilling sand on to the surrounding area is ($\mu$ - coefficient of friction between sand particles)

$\begin{array}{1 1} R \\ \mu R \\ \mu^2 R \\ \frac{R}{\mu}\end{array}$