The maximum efficiency of spiral gears is (where $$\theta $$ = Shaft angle and $$\varphi $$ = Friction angle)

A $$\frac{{\sin \left( {\theta + \varphi } \right) + 1}}{{\cos \left( {\theta - \varphi } \right) + 1}}$$
B $$\frac{{\cos \left( {\theta - \varphi } \right) + 1}}{{\sin \left( {\theta + \varphi } \right) + 1}}$$
C $$\frac{{\cos \left( {\theta + \varphi } \right) + 1}}{{\cos \left( {\theta - \varphi } \right) + 1}}$$
D $$\frac{{\cos \left( {\theta - \varphi } \right) + 1}}{{\cos \left( {\theta + \varphi } \right) + 1}}$$

Correct Answer: $$\frac{{\cos \left( {\theta + \varphi } \right) + 1}}{{\cos \left( {\theta - \varphi } \right) + 1}}$$

Bissoy MCQ
#Mechanical Engineering #Theory of Machine

Related Questions

The radius of a friction circle for a shaft rotating inside a bearing is (where r = Radius of shaft and $$\tan \varphi $$  = Coefficient of friction between the shaft and bearing)
A $${\text{r}}\sin \varphi $$
B $${\text{r}}\cos \varphi $$
C $${\text{r}}\tan \varphi $$
D $$\frac{{\text{r}}}{2}\cos \varphi $$
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 $$\alpha = {90^ \circ } - \varphi $$
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 $$\alpha = {90^ \circ } - \varphi $$
Efficiency of a screw jack is given by (where $$\alpha $$ = Helix angle and $$\varphi $$ = Angle of friction.)
A $$\frac{{\tan \left( {\alpha + \varphi } \right)}}{{\tan \alpha }}$$
B $$\frac{{\tan \alpha }}{{\tan \left( {\alpha + \varphi } \right)}}$$
C $$\frac{{\tan \left( {\alpha - \varphi } \right)}}{{\tan \alpha }}$$
D None of these
In a screw jack, the effort required to lift the load W is given by (where $$\alpha $$ = Helix angle and $$\varphi $$ = Angle of friction)
A $${\text{P}} = {\text{W}}\tan \left( {\alpha - \varphi } \right)$$
B $${\text{P}} = {\text{W}}\tan \left( {\alpha + \varphi } \right)$$
C $${\text{P}} = {\text{W}}\tan \left( {\varphi - \alpha } \right)$$
D $${\text{P}} = {\text{W}}\cos \left( {\alpha + \varphi } \right)$$
Two shafts A and B are made of the same material. The diameter of shaft A is twice as that of shaft B. The power transmitted by the shaft A will be __________ of shaft B.
A Twice
B Four times
C Eight times
D Sixteen times
For a shoe brake, the equivalent coefficient of friction is equal to (where $$\mu $$ = Actual coefficient of friction and $$\theta $$ = Semi-block angle)
A $$\frac{{2\mu \sin \theta }}{{\theta + \sin \theta }}$$
B $$\frac{{\mu \sin \theta }}{{2\theta + \sin 2\theta }}$$
C $$\frac{{4\mu \sin \theta }}{{\theta + \sin \theta }}$$
D $$\frac{{4\mu \sin \theta }}{{2\theta + \sin 2\theta }}$$
When the addenda on pinion and wheel is such that the path of approach and path of recess are half of their maximum possible values, then the length of the path of contact is given by (where r = Pitch circle radius of pinion, R = Pitch circle radius of wheel and $$\varphi $$ = Pressure angle)
A $$\frac{{\left( {{{\text{r}}^2} + {{\text{R}}^2}} \right)\cos \varphi }}{2}$$
B $$\frac{{\left( {{{\text{r}}^2} + {{\text{R}}^2}} \right)\sin \varphi }}{2}$$
C $$\frac{{\left( {{\text{r}} + {\text{R}}} \right)\cos \varphi }}{2}$$
D $$\frac{{\left( {{\text{r}} + {\text{R}}} \right)\sin \varphi }}{2}$$
The natural frequency of free torsional vibrations of a shaft is equal to (where q = Torsional stiffness of the shaft and $$I$$ = Mass moment of inertia of the disc attached at the end of a shaft)
A $$2\pi \sqrt {\frac{{\text{q}}}{I}} $$
B $$2\pi \sqrt {{\text{q}}I} $$
C $$\frac{1}{{2\pi }}\sqrt {\frac{{\text{q}}}{I}} $$
D $$\frac{1}{{2\pi }}$$
The product of the tangential force acting on the shaft and its distance from the axis of the shaft (i.e. radius of shaft) is known as
A Bending moment
B Twisting moment
C Torsional rigidity
D Flexural rigidity

Next steps