Mechanical Operations MCQs

Question 1

Production rate __________ with increased fineness, with a given energy input to the size reduction machine.

Accepted Answer

Decreases

Answer

Increases

Answer

Remains unchanged

Answer

May increase or decrease; depends on the machine

Question 2

Sedimentation on commercial scale occurs in

Accepted Answer

Rotary drum filters

Answer

Classifiers

Answer

Thickeners

Answer

Cyclones

Question 3

A 30% (by volume) suspension of spherical sand particles in a viscous oil has a hindered settling velocity of 4.44 μm/s. If the Richardson Zaki hindered settling index is 4.5, then the terminal velocity of a sand grain is

Accepted Answer

1 μm/s

Answer

0.90 μm/s

Answer

22.1 μm/s

Answer

0.02 μm/s

Question 4

Compressibility co-efficient for an absolutely compressible cake is

Accepted Answer

1

Answer

0

Answer

0 to 1

Answer

∞

Question 5

The work index in Bond's law for crushing of solids has the following dimensions

Accepted Answer

kWh/ton

Answer

No units (dimensionless)

Answer

kW/ton

Answer

$${	ext{kWh}}.{{	ext{m}}^{\frac{1}{2}}}/{	ext{ton}}$$

Question 6

For Indian standard (IS) screens, the mesh number is equal to its aperture size expressed to the nearest deca-micron (0.01 mm). Aperture width of IS screen of mesh number 50 will be approximately __________ microns.

Accepted Answer

500

Answer

5

Answer

50

Answer

5000

Question 7

__________ is the most suitable for compounding rubber and plastic solids.

Accepted Answer

Banbery mixer

Answer

Pan mixer

Answer

Pug mill

Answer

Charge can mixer

Question 8

For spheres, volume shape factor is given by

Accepted Answer

π/6(=V/D³)

Answer

π(=A/D²)

Answer

2π(=2A/D²)

Answer

AD/V

Question 9

Which of the following agitators having a large blade area, rotating at slow speed is used for mixing high viscosity liquids ( > 50000 centipoise)?

Accepted Answer

Helical screw

Answer

Propeller

Answer

Flat blade turbine

Answer

Curved blade turbine