Critical Velocity NEET Questions

Physics - Properties of Solids and Liquids

Critical Velocity MCQ Questions


13.
The Reynolds number Re is defined as:
A.
Re = vd/(ρη)
B.
Re = ηvd/ρ
C.
Re = ρη/(vd)
D.
Re = ρvd/η
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ANSWER :
D. Re = ρvd/η
14.
The Reynolds number is a dimensionless quantity. This can be verified from its formula Re = ρvd/η because:
A.
Only density gives dimensions
B.
It is defined to be dimensionless by convention
C.
All the quantities cancel out
D.
[ρvd/η] = [ML⁻³][LT⁻¹][L]/[ML⁻¹T⁻¹] = [M⁰L⁰T⁰] = dimensionless
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ANSWER :
D. [ρvd/η] = [ML⁻³][LT⁻¹][L]/[ML⁻¹T⁻¹] = [M⁰L⁰T⁰] = dimensionless
15.
The physical significance of the Reynolds number Re = ρvd/η is:
A.
It is the ratio of inertial forces (tending to cause turbulence) to viscous forces (tending to maintain laminar flow)
B.
It measures the compressibility of the fluid
C.
It gives the speed of sound in the fluid
D.
It gives the pressure at the critical point
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ANSWER :
A. It is the ratio of inertial forces (tending to cause turbulence) to viscous forces (tending to maintain laminar flow)
16.
For flow through a pipe of diameter d, the flow is laminar when Re is approximately:
A.
Re between 1000 and 2000
B.
Re > 3000
C.
Re < 1000
D.
Re = exactly 1
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ANSWER :
C. Re < 1000
17.
Turbulent flow definitely occurs when the Reynolds number is:
A.
Re between 1000 and 2000
B.
Re > 2000 (approximately 3000 for pipe flow)
C.
Re = 0
D.
Re < 1000
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ANSWER :
B. Re > 2000 (approximately 3000 for pipe flow)
18.
The critical velocity v_c for flow in a pipe of diameter d is related to the critical Reynolds number Re_c as:
A.
v_c = Re_c × η/(ρd)
B.
v_c = η/(Re_c × ρd)
C.
v_c = Re_c × ρd/η
D.
v_c = Re_c × ρ/(ηd)
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ANSWER :
A. v_c = Re_c × η/(ρd)