# Question #765f8

Dec 17, 2016

(a) Weight of the block is given as $w = m g$
where $g = 9.81 m {s}^{-} 2$ is acceleration due to gravity.
$w = 30 \times 9.81 = 294.3 N$

(b) Pressure $P$ is force per unit area.

$P = \frac{w}{\text{Area}}$

From above expression we see that pressure is inversely proportional to the area in contact.

For maximum pressure the block must be placed with minimum area in contact with the surface on which pressure is to be calculated. As such minimum area is given by lower two sides.
$\therefore {P}_{\text{max}} = \frac{294.3}{0.1 \times 0.4} = 7357.5 N {m}^{-} 2$

Similarly for minimum pressure the block must be placed with maximum area in contact with the surface. Maximum area is given by larger two sides.
$\therefore {P}_{\text{min}} = \frac{294.3}{1.5 \times 0.4} = 490.5 N {m}^{-} 2$