+1 vote
in Machine Kinematics by (38.0k points)
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

1 Answer

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by (106k points)
The correct option is (a) μ > tan α

The explanation: A screw will be self locking if the friction angle is greater than helix angle or coefficient of friction is greater than tangent of helix angle i.e. μ or tan φ > tan α.

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