A lift of mass M = 500kg is descending with speed of 2m s ^ - 1 ....

Given, $u = 2m{s}^{- 1}, a = 2m{s}^{- 2}, s = 6m$

Using kinematics third equation of motion, final speed of lift is ${v}^{2} = {u}^{2} + 2as$

$⇒ v = {2}^{2} + 2\left(2\right)\left(6\right)$

$= 4 + 24 = 28m{s}^{- 1}$

Now, kinetic energy of the lift is $KE = \dfrac{1}{2}m{v}^{2}$

$= \dfrac{1}{2} ( 500 ) 28$

$= 7000J$

$= 7kJ$