Theory Of Machine - Study Mode
[#331] The rotating shafts tend to vibrate violently at whirling speeds because
Correct Answer
(D) Resonance is caused due to the heavy mass of the rotor
[#332] In a screw jack, the effort required to lift the load W is given by (where $$alpha $$ = Helix angle and $$varphi $$ = Angle of friction)
Correct Answer
(B) $${ ext{P}} = { ext{W}} an left( {alpha + varphi }
ight)$$
[#333] The efficiency of a screw jack is maximum, when (where $$alpha $$ = Helix angle and $$varphi $$ = Angle of friction)
Correct Answer
(B) $$alpha = {45^ circ } - frac{varphi }{2}$$
[#334] A body will begin to move down an inclined plane, if the angle of inclination of the plane is ________ the angle of friction.
Correct Answer
(C) Greater than
[#335] The frictional torque transmitted in a conical pivot bearing, considering uniform pressure, is (where R = Radius of shaft and $$alpha $$ = Semi-angle of the cone)
Correct Answer
(B) $$frac{2}{3}mu { ext{WRcosec}}alpha $$