In the diagram $100 \mathrm{~kg}$ block is hanging from a pulley and force $F$ is applied on the string to keep the system in equilibrium. If the whole system is moving up with a constant velocity $v$, then tension at point $P$ in the string will be

• A

  $735 \mathrm{~N}$
• B

  $1050 \mathrm{~N}$
• Correct answer
  C

  $1470 \mathrm{~N}$
• D

  $1200 \mathrm{~N}$

Solution

Tension in each part of the string will be F. Assume tension at point $P$ is $T$.
$\begin{aligned} & T=3 F \\ & 2 F=m g \\ & 2 F=100 \times 9.8 \mathrm{~N} \\ & F=490 \mathrm{~N} \\ & \therefore \quad T=3 \times 490=1470 \mathrm{~N}\end{aligned}$

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