Two heavy bodies of mass 'm' and '3 m' tied together with alight string of mass densityµ are dropped from a helicoper as shown. A constant air friction force 'F' acts on both of them. If the length of the string is l.Determine the time taken by a pulse to go from top to bottom of the string.
(A) l √μ/F
(B) l √2μ/F
(C) l √4μ/F
(D) l √μ/2F
Correct Answer is: (B) l √2μ/F
3mg – (T + F) = 3mg ............. (i)
T + mg – F = ma ............. (ii)
3mg – T – F = 3T + 3mg – 3F
2F = 4T ⇒ T = F/2
