A block and tackle system has 5 pulleys and is 90% efficient. If the effort required to lift a load is 1000 N, the effort required by the system is
Given, Load = 1000 N and η = 90%
We know that, if load moves through a distance 'd', the effort moves through a distance 'nd', where n is the number of pulley in the system.
∴ Velocity Ration (VR) = dEdL=ndd=n=5 [n = 5 (given)]
Also, efficiency is equal to the ratio of mechanical advantage to the velocity ratio i.e.,
η = Mechanical Advantage (MA)Velocity Ratio (VR)
⇒ MA = η× VR
MA = 90100 × 5 = 92
MA = LoadEffort
92 = 1000E
∴ Effort (E) = 20009 = 222.2 N