Week 1: Intro to FS

Which statement best defines a fluid?

• A substance that deforms continuously under any applied shear stress

• A substance that instantly returns to its original shape when shear is removed

• A rigid body that completely resists deformation

• A substance that cannot transmit pressure in all directions

An incompressible fluid is one whose _____ stays essentially constant when pressure changes.

• Density

• Viscosity

• Temperature

• Surface tension

When may the flow of a compressible fluid (e.g., air) be treated as incompressible?

• When density changes is negligible, e.g. Ma < 0.3

• Whenever velocity exceeds speed of sound

• Only at very high pressure

• Never; it must always be treated as compressible

What is the primary characteristic of a viscous fluid?

• It can be compressed easily

• It resists flow and deformation

• It has a constant density regardless of pressure

• It flows freely without resistance

Which of the following best describes a Newtonian fluid?

• Its viscosity remains constant regardless of the shear rate

• Its viscosity changes with the shear rate

• It does not flow under any conditions

• It is a solid at room temperature

What is the effect of temperature on the viscosity of a liquid fluid?

• Viscosity fluctuates randomly with temperature

• Temperature has no effect on viscosity

• Viscosity increases as temperature increases

• Viscosity decreases as temperature increases

The flow of air over an aircraft wing is classified as…

• Internal flow

• External flow

• Open‑channel flow

• Natural convection

Which description matches an open system?

• Volume is fixed and mass may cross

• Mass cannot cross but energy can

• Mass and energy cannot cross the boundary

• Mass can cross the boundary; energy transfer is permitted

Which description matches a closed system?

• Mass can cross the boundary; energy transfer is permitted

• Fixed mass; no mass crosses the boundary but energy may

• Fixed volume; mass may cross

• Variable mass; energy cannot cross

What phenomenon occurs when a liquid rises or falls in a narrow tube due to surface tension?

• Viscosity

• Surface tension

• Hydrostatic pressure

• Capillary action