The mass of a lift is 2000 ~kg . When the tension in the supporting...

Key Idea Apparent weight > actual weight, then the lift is accelerating upward. Here, lift is accelerating upward at the rate of $a$ Hence, equation of motion is written as \begin{gathered}\mathrm{R}-\mathrm{mg}=\mathrm{ma}\\ 28000-20000=2000 \mathrm{a}\\ \Rightarrow \mathrm{a}=\frac{8000}{2000}=4 \mathrm{ ms}^{-2} \text{ upwards } \end{gathered}