Question

The minimum acceleration that must be imparted to the cart in the figure so that the block A will not fall (given $\mu$ is the coefficient of friction between the surfaces of block and cart) is given by:

• A. $\mu g$
• B. $g/\mu$
• C. $\frac{g}{\sqrt{\mu}}$
• D. $\frac{\mu}{g}$

Answer 1

Answer: (B)

The friction force on the block will prevent the block from falling it.
From figure:
$N=ma$ and
$F=mg$
$\Rightarrow \mu\,N=mg$
$\Rightarrow \mu ma=mg$
$\Rightarrow a=g/\mu$