A **uniform cube** of side $a$ sits on a rough incline. As $\theta$ is increased, the cube **topples** before sliding if:

Toppling when CG line crosses the lower edge: $\tan\theta_{\text{topple}} = (a/2)/(a/2) = 1$, so $\theta_{\text{topple}} = 45°$. Sliding when $\tan\theta > \mu$, so $\theta_{\text{slide}} = \arctan \mu$. For toppling first: $\theta_{\text{topple}} < \theta_{\text{slide}}$ ⇒ $1 < \mu$. So a cube on a low-friction surface slides first; only if $\mu > 1$ does it topple before sliding.