Answer
The block will slide before it tips is mu is less than 1/2.
Work Step by Step
We found the following two expressions for theta.
$\theta=tan^{-1}(1/2)$
$\theta = tan^{-1}(\mu)$
We see that the upper expression reflects when the block will tip, and the lower expression reflects when the block will slide. Thus, we see that the block will slide before it tips if mu is less than 1/2.
