Question

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

• A. $500N$
• B. $250N$
• C. $25N$
• D. None of these

Answer 1

The correct option is B $250N$

The force with which the man pulls the rope$=$Tension in the rope$=T$

Thus the tension in the string attached to the platform$=2T$

Normal reaction acts on the man upwards and the platform downwards.

Considering forces acting on the platform,

$Mg+N=2T$

Considering forces acting on the man,

$mg=N+T$

$⟹(M+m)g=3T$

$⟹T=250N$