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If φ is the friction angle, the efficiency of power screw is maximum...

Q.  
If φ is the friction angle, the efficiency of power screw is maximum when the lead angle is


Answer & Explanation

The efficiency of power screw is maximum when the lead angle is,
π/2−φ/2

Thus correct option is: A.

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More Questions Theory of Machines:

Q.  
A wheel of mass m and radius r is in accelerated rolling motion without slip under a steady axial torque T. If the coefficient of kinetic friction is µ the friction force from the ground on the wheel is

A. µmg

B. T/r

C. Zero

D. None of the above


Answer & Explanation

Q.  
A friction circle is drawn when a journal rotates in bearing. Its radius depends on the coefficient of friction and the

A. Magnitude of the forces on the journal

B. Angular velocity of the journal

C. Clearance between the journal and the bearing

D. Radius of the journal


Answer & Explanation

Q.  
Frictional torque for threads at mean radius while raising load is given by

A. WR.tan(φ−α)

B. WR.tan(φ+α)

C. WR.tanα

D. WR.tanφ


Answer & Explanation

Q.  
To ensure self-locking in a screw jack, it is essential that helix angle is

A. Larger than friction angle

B. Smaller than friction angle

C. Equal to friction angle

D. Such as to give maximum efficiency in lifting


Answer & Explanation
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