Machine Design
Which of the following statement is correct regarding power screws?

Both (A) and (B)
The efficiency of a self locking screw can not be more than 50%
The efficiency of Acme (trapezoidal) thread is less than that of a square thread
If the friction angle is less than the helix angle of the screw, then the efficiency will be more than 50%

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Machine Design
In case of thick cylinders, the tangential stress across the thickness of cylinder is

Maximum at the outer surface and minimum at the inner surface
Maximum at the inner surface and zero at the outer surface
Maximum at the inner surface and minimum at the outer surface
Maximum at the outer surface and zero at the inner surface

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