In a footstep bearing, if the radius of the shaft is doubled, then the torque required to overcome the viscous resistance will be

The torque required to overcome viscous resistance of a footstep bearing is (where $$\mu $$ = Viscosity of the oil, N = Speed of the shaft, R = Radius of the shaft and t = Thickness of the oil film)

A

$$\frac{{\mu {\pi ^2}{\text{NR}}}}{{60{\text{t}}}}$$

B

$$\frac{{\mu {\pi ^2}{\text{N}}{{\text{R}}^2}}}{{60{\text{t}}}}$$

C

$$\frac{{\mu {\pi ^2}{\text{N}}{{\text{R}}^3}}}{{60{\text{t}}}}$$

D

$$\frac{{\mu {\pi ^2}{\text{N}}{{\text{R}}^4}}}{{60{\text{t}}}}$$

In a footstep bearing, if the speed of the shaft is doubled, then the torque required to overcome the viscous resistance will be

A

Double

B

Four times

C

Eight times

D

Sixteen times

The torque required to overcome viscous resistance of a collar bearing is (where R₁ and R₂ = External and internal radius of collar)

A

$$\frac{{\mu {\pi ^2}{\text{N}}}}{{60{\text{t}}}}\left( {{{\text{R}}_1} - {{\text{R}}_2}} \right)$$

B

$$\frac{{\mu {\pi ^2}{\text{N}}}}{{60{\text{t}}}}\left( {{\text{R}}_1^2 - {\text{R}}_2^2} \right)$$

C

$$\frac{{\mu {\pi ^2}{\text{N}}}}{{60{\text{t}}}}\left( {{\text{R}}_1^3 - {\text{R}}_2^3} \right)$$

D

$$\frac{{\mu {\pi ^2}{\text{N}}}}{{60{\text{t}}}}\left( {{\text{R}}_1^4 - {\text{R}}_2^4} \right)$$

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 power absorbed (in watts) in overcoming the viscous resistance of a footstep bearing is

A

$$\frac{{\mu {\pi ^3}{{\text{N}}^2}{{\text{R}}^2}}}{{1800{\text{t}}}}$$

B

$$\frac{{\mu {\pi ^3}{{\text{N}}^2}{{\text{R}}^4}}}{{1800{\text{t}}}}$$

C

$$\frac{{\mu {\pi ^3}{{\text{N}}^2}{{\text{R}}^2}}}{{3600{\text{t}}}}$$

D

$$\frac{{\mu {\pi ^3}{{\text{N}}^2}{{\text{R}}^4}}}{{3600{\text{t}}}}$$

A 10 kW, 400 V, 3-phase, 4-pole, 50 Hz induction motor develops the rated output at rated voltage with its slip rings shorted. The maximum torque is twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit. An external resistance is now tripled in the rotor circuit. Then the slip at which maximum torque occur for the same load torque is?

A

0.3

B

0.268

C

0.03

D

3

In a mine between upcast shaft and downcast shaft, two airways are connected in parallel and their resistances are 100 and 120 Ns^-2m^-8 respectively. The resistance of upcast shaft, downcast shaft and the fan drifts are 10, 20, and 5 Ns^-2m^-8 respectively. The rate of airflow through the split airway having resistance of 100 Ns^-2m^-8 in m³/s is

A

0.42

B

0.79

C

2.19

D

7.90

E

270.06

A double universal joint is used to connect two shafts in the same plane. The intermediate shaft is inclined at an angle of 20° to the driving shaft as well as the driven shaft. Find the maximum speed of the intermediate shaft if the driving shaft has a constant speed of 500 r.p.m.

A

532.1 r.p.m

B

469.85 r.p.m

C

566.25 r.p.m

D

441.5 r.p.m.

A double universal joint is used to connect two shafts in the same plane. The intermediate shaft is inclined at an angle of 20° to the driving shaft as well as the driven shaft. Find the minimum speed of the intermediate shaft if the driving shaft has a constant speed of 500 r.p.m.

A

532.1 r.p.m

B

469.85 r.p.m.

C

566.25 r.p.m.

D

441.5 r.p.m.

A double universal joint is used to connect two shafts in the same plane. The intermediate shaft is inclined at an angle of 20° to the driving shaft as well as the driven shaft. Find the maximum speed of the driven shaft if the driving shaft has a constant speed of 500 r.p.m.

A

532.1 r.p.m

B

469.85 r.p.m.

C

566.25 r.p.m.

D

441.5 r.p.m.

In a footstep bearing, if the radius of the shaft is doubled, then the torque required to overcome the viscous resistance will be

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