Phys 1011Freshman (1st Year)Engineering & Technology

Fluid Mechanics & Bernoulli's Equation

Continuity equation, Bernoulli's energy theorem, Torricelli's law, and venturi flow meter applications in Ethiopian freshman engineering physics.

MoE National Competency Objectives
  • State and derive the equation of continuity for incompressible laminar flow.
  • Derive Bernoulli's equation from the work-energy theorem.
  • Solve practical problems involving Venturi tubes, Pitot tubes, and siphon flow.
  • Analyze exit exam level multiple-choice questions on viscous and non-viscous fluid dynamics.

Essential Governing Formulas & Theorems

Continuity Equation
A1v1=A2v2=Q=constantA_1 v_1 = A_2 v_2 = Q = \text{constant}

Q represents volume flow rate in m^3/s for incompressible fluids.

Bernoulli's Energy Equation
P1+12ρv12+ρgh1=P2+12ρv22+ρgh2P_1 + \frac{1}{2} \rho v_1^2 + \rho g h_1 = P_2 + \frac{1}{2} \rho v_2^2 + \rho g h_2

Applies along a streamline for steady, non-viscous, incompressible flow.

Torricelli's Efflux Velocity
v=2ghv = \sqrt{2 g h}

Speed of effluent liquid discharging through a small orifice under gravity.

Exit Exam & Midterm Practice Questions

Full step-by-step solutions with theoretical proofs

1 Questions
Q1MoE Freshman Common Exam (Addis Ababa University)
medium
Water flows horizontally through a pipe that narrows from an area of 0.04 m20.04\text{ m}^2 with velocity 2.0 m/s2.0\text{ m/s} to an area of 0.01 m20.01\text{ m}^2. If the pressure in the wider section is 150 kPa150\text{ kPa}, what is the pressure in the narrow section? (Assume water density ρ=1000 kg/m3\rho = 1000\text{ kg/m}^3)
A
120 kPa
B
90 kPa
C
180 kPa
D
60 kPa
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