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

Both (A) and (B)
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%
The efficiency of a self locking screw can not be more than 50%

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Machine Design
When a machine member is subjected to torsion, the torsional shear stress set up in the member is

Zero at both the centroidal axis and outer surface of the member
Maximum at the centroidal axis and zero at the outer surface of the member
Zero at the centroidal axis and maximum at the outer surface of the member
Maximum at both the centroidal axis and outer surface of the member

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Machine Design
In case of V belt drive

The belt should touch the bottom of groove in the pulley
The belt should not touch the sides of groove in the pulley
None of these
The belt should not touch the bottom of groove in the pulley

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