Given: L = 5 kgf, Load arm = 20 cm, Effort arm = 100 – 20 = 80 cm.
(Since the crow bar is the lever of first order with fulcrum in between the load and the effort).
(i) Mechanical advantage = Effort arm/Load arm = 80/20 = 4
(ii) M.A. = Load(L)/Effort(E)
∴ Effort = Load(L)/M.A. = 5/4
= 1.25 kgf.