Physics

Basic Concepts of Physics

• Temperature

  • Definition: Temperature is a measure of the kinetic energy of molecules.

  • Kinetic Energy: Energy of motion, exemplified by a moving car that has stored kinetic energy until it hits an object (e.g., tree).

  • Effect of Temperature: As temperature increases, the speed and kinetic energy of molecules in a substance increase.

Heat Transfer Methods

• Convection

  • Definition: Transfer of heat due to the movement of fluids (e.g., hot air rising).

• Conduction

  • Definition: Heat transfer through direct contact of molecules (e.g., a hot stove heating surrounding areas).

• Radiation

  • Definition: Transfer of heat without needing a medium (e.g., sun heating the ground).

• Diffusion

  • Definition: Mixing of molecules and does not transfer heat.

Pressure of Gases in Containers

• Boyle's Law

  • Definition: Relates pressure, temperature, and volume of a gas.

  • Key Relationship: Pressure is determined by the ratio of temperature to volume (P = k * (T/V)).

  • Implications:

    • If temperature stays constant and volume doubles, pressure decreases.

    • If both volume and temperature double, pressure remains the same.

Properties of Liquids

• Incompressibility

  • Definition: Liquids cannot be compressed; when more liquid is added to a confined space at constant temperature, pressure increases significantly.

• Boiling Point

  • Dependence on Pressure: Varies with surrounding pressure (lower at high altitudes, higher at sea level).

Speed of Sound and Air Density

• Speed of Sound

  • Factors: Changes with temperature; colder air slows sound waves.

• Humidity

  • Absolute Humidity: Actual amount of water vapor in the air.

  • Relative Humidity: Ratio of actual water vapor to the saturation amount at a given temperature and pressure.

  • Dew Point: Temperature at which air becomes saturated with water vapor.

  • Density: Humid air is less dense than dry air due to the lighter weight of water vapor.

Effects of Temperature and Humidity on Aircraft

• Landing Speed

  • Higher temperatures and humidity result in greater true landing speed since air is less dense.

Bernoulli's Principle

• Fluid Dynamics

  • As air flows through a narrowed area, it speeds up, causing pressure to decrease. This relationship helps in measuring flow rate.

  • Application in Aircraft Wings:

    • Air travels faster over the top surface, creating lower pressure compared to the bottom, thus generating lift.

    • Downwash: Air is deflected downward during lift, contributes to upward force on the wing.

Wing Design Concepts

• Aspect Ratio

  • Definition: Ratio of wingspan to average chord.

  • High Aspect Ratio: Long, narrow wings favored in gliders for low stall speed.

• Wing Planform

  • Rectangular Wings: Stall at root first, maintaining aileron control and providing stall warning.

• Winglets

  • Purpose is to reduce drag and increase lift-to-drag ratio by minimizing wing tip vortices.

• Dihedral Wings

  • Wing tips are angled upward, enhancing lateral stability during flight.

Work and Power

• Work

  • Definition: Work equals force times distance (W = F x D).

  • Example Question: Moving a 20 lb weight 3 feet requires 60 foot-pounds of work (W = 20 x 3).

• Power

  • Definition: Work done per unit of time. More power is needed to do work faster.

  • Horsepower: 1 horsepower = 33,000 foot-pounds per minute.

Mechanical Advantage and Simple Machines

• Pulleys and Inclined Planes

  • Use of simple machines spreads work over longer distances, requiring less force.

  • Example: Moving a barrel up a ramp requires force inversely proportional to the ramp's length-to-height ratio.

• Hydraulic Systems

  • Governed by Pascal’s Law: F = P x A (force equals pressure times area).

  • Example Question: Calculating force produced by a hydraulic piston based on pressure and effective area.