fig 4 represents a block-and-tackle pulley system on which an effort of W newtons supports a load of 120.0N if the efficiency of the system is 40% then the value of W is
A.
28.0N
B.
48.0N
C.
50.0N
D.
288.0N
Correct answer is C
Efficiency = \(frac{M.A×100}{V.R}\)
V.R = 6
40= \(frac{M.A×100}{6}\)
M.A = \(frac{6 ×40}{100}\)
M.a=2.4
M.A= \(frac{L}{E\)
E= \(frac{120}{2.4\)
E= 50