The efficiency of a screw jack is maximum, when (where $$\alpha $$ = Helix angle and $$\varphi $$ = Angle of friction)
A. $$\alpha = {45^ \circ } + \frac{\varphi }{2}$$
B. $$\alpha = {45^ \circ } - \frac{\varphi }{2}$$
C. $$\alpha = {90^ \circ } + \varphi $$
D. $$\alpha = {90^ \circ } - \varphi $$
Answer: Option B
This Question Belongs to Mechanical Engineering >> Theory Of Machine
In considering friction of a V-thread, the virtual coefficient of friction (μ1) is given by
A. μ1 = μsinβ
B. μ1 = μcosβ
C. $${\mu _1} = \frac{\mu }{{\sin \beta }}$$
D. $${\mu _1} = \frac{\mu }{{\cos \beta }}$$
The lower pairs are _________ pairs.
A. Self-closed
B. Force-closed
C. Friction closed
D. None of these
In a coupling rod of a locomotive, each of the four pairs is a ________ pair.
A. Sliding
B. Turning
C. Rolling
D. Screw
A kinematic chain is known as a mechanism when
A. None of the links is fixed
B. One of the links is fixed
C. Two of the links are fixed
D. None of these
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