Physics
Core content
Physics for avionics maintenance covers SI units, scalars and vectors, kinematics, Newton's laws, work, energy and power, momentum, pressure and density, fluid flow, temperature and heat, gas laws, basic optics, and wave motion. You should distinguish mass from weight, gauge pressure from absolute pressure, and static pressure from dynamic pressure. Understand that force is a vector, that equilibrium means zero net force and zero net moment, and that energy is conserved but not always usefully converted. In fluids, pressure acts equally in all directions at a point, and Bernoulli's relationship links higher velocity with lower static pressure in a streamline.
Traps
Questions often mix mass and weight, or use gauge pressure where absolute pressure is required. Absolute pressure equals gauge pressure plus atmospheric pressure. Another trap is treating temperature as heat: a large mass at a low temperature can contain more thermal energy than a small mass at a high temperature. In wave questions, frequency is fixed by the source and speed depends on the medium. In optics, the angle of incidence equals the angle of reflection, but refraction bends toward the normal when entering a denser medium.
Worked example
Find the weight of a 25 kg unit at g = 9.81 m/s squared. Weight = mass x gravitational acceleration = 25 x 9.81 = 245.25 N. If the same unit is on a bench, its mass remains 25 kg; only the weight force changes with gravity. Rule of thumb: absolute pressure = gauge pressure + atmospheric pressure, with all terms in the same units.
Key points
- Mass is measured in kilograms; weight is a force in newtons.
- Gauge pressure plus atmospheric pressure gives absolute pressure.
- Bernoulli: higher flow velocity means lower static pressure along a streamline.
- Frequency is set by the source; wave speed depends on the medium.
- Equilibrium requires zero net force and zero net moment.