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

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

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Machine Design
When the shaft rotates in anticlockwise direction at high speed in a bearing, it will

Move towards right of the bearing making no metal to metal contact
Have contact at the bottom most of the bearing
Move towards right of the bearing making metal to metal contact
Move towards left of the bearing making metal to metal contact

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