Question

In the given a diagram with what force must the man pull the rope to hold the plank in position? Weight of the man is 60 kgf. (Neglect the weight of plank, rope and pulley)

• A. 15 kgf
• B. 30 kgf
• C. 60 kgf
• D. 120 kgf

Answer 1

Answer: (A)

15 kgf

From the fig,

$T=T^1+T^1=2T^1.......\left(1\right)$

$R=T+T^1......\left(2\right)$

$R+T^1=mg......\left(3\right)$

$\left(2\right)-\left(3\right),R-R-T^1=T+T^1-mg$

$mg=2T^1+2T^1$ (as $T=2T^1$)

$4T^1=60$

$T^1=15kgf$