# A fireman has to carry an injured person of mass 40 kg from the top of a building with the help of the rope which can with stand a load of 100 kg. The acceleration of the fireman if his mass is 80 kg will be

$(a)\;8.17 m/s^2 \quad (b)\; 9.8 m/s^2 \quad (c)\;17.97 m/s^2 \quad(d)\;1.63 m/s^2$

Total mass $= 80+40=120 kg$
The rope cannot withstand this load
So he has to slide down with an acceleration.
Maximum tension $=100 \times 9.8\; N$
$m(g-a)=100 \times 9.8$
$120 (9.8-a)=980$
$=>a=1.63\; m/s^2$
Hence d is the correct answer.

edited Jan 26, 2014 by meena.p