$1\mathrm{.}1($Elliott P$2\mathrm{.}9)$ Consider a block of concrete weighing $1kg.$

$($a$)$ How far must it fall to change its potential energy by $1kJ?($ANS$.100m)$

$($b$)$ What would be the value of its velocity at that stage? $($ANS$.44\mathrm{.}7\frac{m}{s})$