Applied Physics Study Guide
Applied physics is core physics wearing work clothes: the same Newton's laws, energy books, and Maxwell's equations, pointed at cars, phones, power grids, and medical scanners. This guide maps the principles to the technologies.
Key formulas
Bernoulli's Equation — P + ½ρv² + ρgh = constant
Along a streamline, pressure plus kinetic-energy density plus gravitational-energy density stays constant.
Ideal Gas Law — PV = nRT
Pressure times volume equals moles times the gas constant times absolute temperature.
Kinetic Energy Formula — KE = ½mv²
Kinetic energy equals one-half times mass times velocity squared.
Newton's Second Law — F = ma
The net force on an object equals its mass times its acceleration.
Ohm's Law — V = IR
Voltage equals current times resistance.
Power Formula — P = W/t
Power equals work done divided by the time taken.
Topic checklist
Motion and forces in machines
Apply to vehicles, structures, and machines.
Estimate stopping distances with .
Explain crumple zones with impulse and momentum.
Energy and power in technology
Track energy conversions: chemical to kinetic to heat in engines.
Use to compare motors and engines.
Compute efficiency as useful output over total input.
Electricity in everyday devices
Apply and to household circuits.
Explain why power lines use high voltage (less loss).
Size fuses and breakers from expected currents.
Thermodynamics of engines and climate
Use for engines, tires, and weather balloons.
Explain refrigeration as controlled heat pumping.
Relate the Carnot limit to real engine efficiencies.
Fluids in engineering
Apply Bernoulli to wings, sails, and ventilation.
Explain buoyancy in ships, submarines, and hot-air balloons.
Use for dams and diving.
Modern physics in technology
Describe semiconductors, sensors, and fiber optics qualitatively.
Explain GPS time corrections from relativity.
Give the physics inside one medical device (MRI, X-ray, or ultrasound).
Common mistakes
Mistake: Assuming energy technologies are perfectly efficient.
Fix:
Regenerative braking recovers some kinetic energy, but friction and air drag always waste part of it — efficiency is never 100%. Track where each joule goes instead of assuming perfect recovery.
Mistake: Thinking high-voltage transmission is wasteful.
Fix:
Power lines step voltage up to hundreds of kilovolts precisely so current (and heating) stays small for the same delivered power. High voltage is a feature, not a hazard to eliminate.
Mistake: Believing safety features defy physics rather than exploit it.
Fix:
ABS and airbags manage the impulse: longer stopping time means smaller peak force on you. The car is designed to sacrifice itself over centimeters so your body stops over a survivable distance.
Mistake: Dismissing relativity as irrelevant to engineering.
Fix:
GPS satellites tick faster by about 38 microseconds per day (weaker gravity wins over their speed). Uncorrected, positions would drift kilometers within a day — relativity is an engineering requirement.
Mistake: Thinking insulation generates heat.
Fix:
Insulation slows heat flow; it does not create warmth. A thermos keeps cold drinks cold for the same reason it keeps hot drinks hot — it resists transfer in both directions.
Exam tips
Connect every device back to a core principle: which conservation law or force law is at work?
Estimate first: round numbers reveal whether an answer is plausible before precise math.
In efficiency problems, define 'useful output' explicitly before dividing.
For 'explain how it works' questions, structure answers as energy conversions in order.