A screw jack has square threads and the lead angle of the thread is α. The screw jack will be self locking when the coefficient of friction (μ) is
(a) μ > tan α
(b) μ = sin α
(c) μ = cot α
(d) μ = cosec α
The question was posed to me by my school teacher while I was bunking the class.
Question is taken from Efficiency of Self Locking Screws in portion Friction of Machine Kinematics