6 - FLUIDS

• What is a fluid?

  Collection of randomly arranged molecules
• What are the two divisions of fluid mechanics?

  Fluid statics and fluid dynamics
• What does mass density (ρ) determine in fluids?

  It determines the behavior of the fluid
• How is mass density (ρ) calculated?

  ρ = $\frac{m}{V}$
• What is the SI unit of mass density?

  [kg/m³]
• What is the mass of blood in a man weighing 690 N with a density of 1060 kg/m³ and volume of $5.2 \times 10^{-3} m³$?


  5.5 kg
• What is the weight of the blood calculated from its mass?

  54 N
• What percentage of body weight does the blood contribute?

  7.8%
• What is specific gravity (S.G.)?

  Ratio of density of a substance to water
• What is the unit of specific gravity?

  Unitless
• What does S.G. < 1 indicate?

  Substance floats on the reference fluid
• What does S.G. > 1 indicate?

  Substance sinks in the reference fluid
• How is pressure defined in fluid mechanics?

  Force per unit area
• What type of stress can be exerted on an object in a static fluid?

  Only compressive stress
• What is the formula for pressure (P) in fluid mechanics?

  �� = $\frac{F}{A}$
• What is the SI unit of pressure?

  Pascal (Pa)
• What does it mean that fluid pressure is independent of area and shape?

  Water seeks its own level
• What is the volume of water in a mattress measuring 2.00 m by 2.00 m and 30.0 cm deep?

  1.2 m³
• What is the mass of water in the mattress with a density of 1000 kg/m³?

  1.2 x 10³ kg
• What is the weight of the water in the mattress?

  1.18 x 10⁴ N
• Why should a waterbed be placed on a sturdy floor?

  It has a large weight load
• How does water pressure change with depth?

  Water pressure increases with depth
• What happens to atmospheric pressure with increasing altitude?

  It decreases with increasing altitude
• What is the formula for pressure at a depth h in a fluid?

  𝑃 = ��₀ + ρ𝑔ℎ
• What does Pascal's Law state?

  Pressure change is transmitted undiminished
• How does a hydraulic press work?

  It uses pressure to amplify force
• What is the relationship between forces in a hydraulic press?

  P = $\frac{F_1}{A_1} =$$\frac{F_2}{A_2}$
• What force must be exerted to lift a car weighing 13,300 N using a hydraulic press?

  1.48 x 10³ N
• What air pressure is needed to produce a force of 1.48 x 10³ N in a hydraulic press?

  1.88 x 10⁵ Pa
• What is buoyant force (B)?

  Upward force exerted by a fluid
• What does Archimedes' principle state?

  B buoyant force equals weight of displaced fluid
• What does positive buoyancy mean?

  Object floats because displaced water weighs more
• What does negative buoyancy mean?

  Object sinks because it weighs more
• What is neutral buoyancy?

  Object neither sinks nor floats
• What are the key concepts of fluid mechanics?

  • Fluid statics: mechanics of fluids at rest
  • Fluid dynamics: mechanics of fluids in motion
  • Mass density: behavior of fluids
  • Specific gravity: comparison of densities
  • Pressure: force per unit area
  • Buoyant force: upward force on immersed objects
• What are the applications of Pascal's Law?

  • Hydraulic press
  • Hydraulic brakes
  • Car lifts
  • Hydraulic jacks
  • Forklifts
• What are the types of buoyancy?

  • Positive buoyancy: object floats
  • Negative buoyancy: object sinks
  • Neutral buoyancy: object neither sinks nor floats
• What does it mean for an object to be positively buoyant?

  It floats because it displaces more water weight
• Why does a boat float even if it weighs more than the water it displaces?

  Its size and shape allow it to displace more water
• If a boat weighs 50 lbs and displaces 100 lbs of water, what can be said about its buoyancy?

  It is positively buoyant and will float