Resistances R, 2R, 4R, 8R......`intfy`are connected in parallel. What is their equivalent resistance?

Explanation

External forces acting on the system are weights of the men, weight of the ladder and tension supporting the ladder. Denotingmasses of men A,B,C and ladder by `m_(A), m_(B), m_(C) and m_(L)`, accelaration due to gravity by g, tension in the string by T and accelarations of the men A,B,C and ladder by `a_(A), a_(B), a_(c)` and `a_(L)` respectively, we can write the following equation according to equation.
`Sigma vec(F)_(1) = sigma(m_(1)vec(a)_(1))rarr" " T-m_(A)g - m_(B) g - m_(C ) g - m_(L)g = m_(A)a_(A) + m_(B)a_(B) + m_(C )a_(C ) + m_(L)a_(L)`
Substituting given values of masses `m_(A) = 40 kg, m_(B) = 60 kg, m_(C ) = 50 kg, m_(L) = 20kg`, given values of accelarations `g=10m//s^(2), a_(A) = -2m//s^(2),a_(B)=0m//s^(2), ac=1m//s^(2)`, and `a_(L) = 0m//s^(2)`, we obtain `T-400-600-500-200=-80+0+50+0`
`T=1670N`