Machine Design
In an oil lubricated journal bearing, the coefficient of friction between the journal and the bearing

Is minimum at zero speed and increases monotonically with increase in speed
Becomes minimum at an optimum speed and then increases with further increase in speed
Is maximum at zero speed and decreases monotonically with increase in speed
Remains constant at all speeds

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Machine Design
The ends of the leaves of a semi-elliptical leaf spring are made triangular in order to

Have variable bending moment (M) in each leaf
Make M/I constant throughout the length of the leaf
Obtain variable moment of inertia (I) in each leaf
Permit each leaf to act as an overhanging beam

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Machine Design
Split nut is a locking device in which

Through slots are made at top and a cotter pin is passed through these and a hole in the bolt, and cotter pin splitted and bent in reverse direction at the other end
A slot is cut partly in middle of nut and then slot reduced by tightening screw
One smaller nut is tightened over main nut and main nut tightened against smaller one by loosening, creating friction jamming
A hard fibre or nylon cotter is recessed in the nut and becomes threaded as the nut is screwed on the bolt causing a tight grip

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