Mechanical Engineering

The value of Biot number is very small (less then 0.1)
  • a)
    the convective resistance of fluid is negligible
  • b)
    the conductive resistance of the fluid is negligible
  • c)
    the conductive resistance of the solid is negligible
  • d)
    none of these
Correct answer is option 'C'. Can you explain this answer?

SANSKAR ANAND answered  •  3 hours ago
Since Biot number is the ratio of conduction resistance to convection resistance and in lumped heat analysis convection resistance ≫ conduction resistance, it means that conduction resistance of solid is negligible as compared to convection resistance of fluid.

The maximum values of Poisson’s ratio for an elastic material is
  • a)
    0.25
  • b)
    0.5
  • c)
    0.75
  • d)
    1.0
Correct answer is option 'B'. Can you explain this answer?

NEERAJ KUMAR answered  •  3 hours ago
Poisson’s ratio lies between 0 to 0.5.
μ = 0.5 for pure elastic rubber
μ = 0.1 to 0.2 for concrete
μ = 0.25 to 0.33 for steel

Circulation of water is by natural convection currents in
  • a)
    LaMont boiler
  • b)
    Benson boiler
  • c)
    Velox boiler
  • d)
    Babcock-Wiicox boiler
Correct answer is option 'D'. Can you explain this answer?

KSHIT RAJ answered  •  3 hours ago
LaMont, Benson and Veiox are high pressure boilers which use in external pump to force wate or steam through the boiler circuit independen of natural circulation due to static head anc convection currents.

If Pa and Pv denote respectively the partial pressure of dry air and that of water vapour in moist air, the specific humidity of air is given by
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'C'. Can you explain this answer?

SINGH AMIT answered  •  3 hours ago
Assuming that the dry air and water vapour behaves as perfect gases, we have for dry 

For water vapour

Also


Ra = 0.287 kJ/kgK (for dry air)
Rv = 0.461 kJ/kgK (for water vapour)

Which is not the advantage of wet friction clutch?
  • a)
    high coefficient of friction
  • b)
    simplicity of sealing
  • c)
    greater operating life
  • d)
    smoothness in operation and engagement
Correct answer is option 'A'. Can you explain this answer?

RAHUL KUMAR answered  •  14 hours ago
• The we friction is about one-third of dry friction clutch.
• The torque capacity of dry clutch is more as compared with the torque capacity of wet clutch of the same dimensions.
• In wet clutches, the lubricating oil carries away the frictional heat.

Identify the type of rivet head usually used for boiler plate riveting:
  • a)
    pan head
  • b)
    snap head
  • c)
    counter sunk head
  • d)
    conical head
Correct answer is option 'B'. Can you explain this answer?

SUDHANSHU SHARMA answered  •  14 hours ago
The snap heads are usually employed for structural work and machine riveting. The counter sunk heads are mainly used for ship building where flat surfaces are necessary. The conical heads (also known as conidal heads) are mainly used in case of hand hammering. The pan heads have maximum strength, but these are difficult to shape.

Particle A makes a perfectly elastic collision with another particle B at rest. They fly apart in opposite direction with equal speeds. The ratio of their masses is
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'C'. Can you explain this answer?

NEERAJ DUBEY answered  •  14 hours ago
m1 = mA, m2 = mB, u1 = u, u2 = 0, v1 =v, v2 = - v
    By principle of conservation of linear momentum.
    m1 u 0 = m1 V m2 (-v) = (m1 – m2) v
    By principle of conservation of K.E.
 

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