A lift is tied with thick iron ropes having mass ‘M’. The maximum acceleration of the lift is ‘a’ $m/s^2$ and maximum safe stress is ‘S’ $N/m^2$ . The minimum diameter of the rope is

• A

  ${\left[\frac{6M\left(g+a\right)}{\pi S}\right]}^{\frac{1}{2}}$
• Correct answer
  B

  ${\left[\frac{4M\left(g+a\right)}{\pi S}\right]}^{\frac{1}{2}}$
• C

  ${\left[\frac{M\left(g+a\right)}{\pi S}\right]}^{\frac{1}{2}}$
• D

  ${\left[\frac{M\left(g-a\right)}{\pi S}\right]}^{\frac{1}{2}}$

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