The mass of a lift is $2000 \mathrm{~kg}$. When the tension in the supporting cable is $28000 \mathrm{~N}$, then its acceleration is

• A

  $30 \mathrm{~ms}^{-2}$ downwards
• Correct answer
  B

  $4 \mathrm{~ms}^{-2}$ upwards
• C

  $4 \mathrm{~ms}^{-2}$ downwards
• D

  $14 \mathrm{~ms}^{-2}$ upwards

Solution

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 $$ \begin{gathered} \mathrm{R}-\mathrm{mg}=\mathrm{ma} \\ 28000-20000=2000 \mathrm{a} \\ \Rightarrow \mathrm{a}=\frac{8000}{2000}=4 \mathrm{~ms}^{-2} \text { upwards } \end{gathered} $$

Hence, the correct answer is option: 'B'.