Question

A $50kg$ person stand on a $25kg$ platform. He pulls on the rope which is attached to the platform via the frictionless pulleys as shown in the figure. The platform moves upwards at a steady rate if the force (in $N$) with which the person pulls the rope is

Answer 1

Step1: Draw FBD of plank and man

Step2: Find fore equation for man and plank
$T+N=Mg\dots \dots \left(i\right)$

$2T=N+mg\dots \dots \left(ii\right)$

Step3: Find tension in the string
Force applied by man will itself become the tension
So, to find tension, substitute $N$ from equation $\left(i\right)$ in equation $\left(ii\right)$,

$2T=(Mg-T)+mg$

$3T=(M+m)g$

$3T=(50+25)\times 10$

$T=250N$

FINAL ANSWER: $250$