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

In an oil lubricated journal bearing, the coefficient of friction between the journal and the bearing

A

Remains constant at all speeds

B

Is minimum at zero speed and increases monotonically with increase in speed

C

Is maximum at zero speed and decreases monotonically with increase in speed

D

Becomes minimum at an optimum speed and then increases with further increase in speed

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

$$\frac{{\text{r}}}{2}\cos \varphi $$

In a journal bearing, the load on the bearing is __________ to the axis of the journal.

A

Parallel

B

Perpendicular

C

Both A and B

D

None of these

In a partial journal bearing, the angle of contact of the bearing with the journal is

A

120°

B

180°

C

270°

D

360°

In a full journal bearing, the angle of contact of the bearing with the journal is

A

120°

B

180°

C

270°

D

360°

The frictional torque transmitted in a flat pivot bearing, considering uniform wear, is (where μ = Coefficient of friction, W = Load over the bearing and R = Radius of bearing surface)

A

$$\frac{1}{2}$$μWR

B

$$\frac{2}{3}$$μWR

C

$$\frac{3}{4}$$μWR

D

μWR

If p = bearing pressure on projected bearing area, Z = absolute viscosity of lubricant and N = speed of journal, then the bearing characteristic number is given by

A

$$\frac{{{\text{ZN}}}}{{\text{p}}}$$

B

$$\frac{{\text{p}}}{{{\text{ZN}}}}$$

C

$$\frac{{\text{Z}}}{{{\text{pN}}}}$$

D

$$\frac{{\text{N}}}{{{\text{Zp}}}}$$

When the length of the journal is equal to the diameter of the journal, then the bearing is said to be a

A

Short bearing

B

Long bearing

C

Medium bearing

D

Square bearing

In a boundary lubricated bearing, there is a __________ of lubricant between the journal and the bearing.

A

Thick film

B

Thin film

C

Either A or B

D

None of these

A sliding bearing which can support steady loads without any relative motion between the journal and the bearing, is called

A

Hydrostatic lubricated bearing

B

Hydrodynamic lubricated bearing

C

Boundary lubricated bearing

D

Zero film bearing

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

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