Physics for Aviation — practice questions

8% of the exam ≈5 real questions 5 free questions here

Eight percent of the weighting: work and machines, pressure, heat, Bernoulli and Newton, the gas laws, force-area-pressure, the standard atmosphere and humidity, and basic aerodynamics and flight controls.

Where people lose points

• Absolute pressure = gauge + 14.7 psi on a standard day.
• Charles's law works only with ABSOLUTE temperature (kelvin or rankine), never °F or °C.
• Humid air is LESS dense than dry air, so it reduces takeoff and engine performance.
• Angle of attack is chord line to relative wind; chord line to fuselage axis is the angle of incidence.
• Ailerons roll about the longitudinal axis, the elevator pitches about the lateral axis, the rudder yaws about the vertical axis.

Questions and answers, explained

All 5 questions above, with the correct answer and why it is correct. Everything here is on physics for aviation.

1. A technician pushes a parts cart 20 feet with a steady force of 50 pounds. How much work is done?

   • A70 foot-pounds
   • B2.5 foot-pounds
   • C1,000 foot-poundsCorrect
   • D10,000 foot-pounds

   Why: Work = force × distance = 50 lb × 20 ft = 1,000 ft-lb. Work involves no time; how fast it is done is power.

   Reference AM.I.J.K2 · FAA-H-8083-30B, Ch. 5 (Work)

2. A gauge reads 30 psi on a standard day at sea level. What is the absolute pressure?

   • A15.3 psia
   • B30.0 psia
   • C59.9 psia
   • D44.7 psiaCorrect

   Why: Gauge pressure reads zero at atmospheric pressure. Absolute pressure = gauge pressure + atmospheric pressure = 30 + 14.7 = 44.7 psia on a standard day.

   Reference AM.I.J.K4 · FAA-H-8083-30B, Ch. 5 (Pressure; Absolute Pressure)

3. The thrust of a turbojet engine is best explained by which of Newton's laws?

   • AThe first law, inertia
   • BThe law of universal gravitation
   • CThe second law alone, with no reaction
   • DThe third law, action and reactionCorrect

   Why: Newton's third law: for every action there is an equal and opposite reaction. The engine accelerates a mass of air rearward, and the reaction pushes the engine and aircraft forward.

   Reference AM.I.J.K6 · FAA-H-8083-30B, Ch. 5 (Newton's Third Law)

4. A hydraulic system pressure of 1,000 psi acts on an actuator piston with an area of 2 square inches. What force does the piston produce?

   • A500 pounds
   • B1,002 pounds
   • C4,000 pounds
   • D2,000 poundsCorrect

   Why: Force = pressure × area = 1,000 psi × 2 sq in = 2,000 lb. Pascal's law: pressure in an enclosed fluid acts equally in all directions, so a larger piston produces proportionally more force.

   Reference AM.I.J.K13 · FAA-H-8083-30B, Ch. 5 (Force, Area, and Pressure; Pascal's Law)

5. Angle of attack is the angle between

   • Athe wing chord line and the fuselage centerline
   • Bthe wing and the horizon as seen from the side
   • Cthe wing chord line and the relative windCorrect
   • Dthe wing's upper and lower surfaces at the tip

   Why: Angle of attack is measured between the chord line and the relative wind. The fixed angle between the chord line and the fuselage's longitudinal axis is the angle of incidence, a different thing.

   Reference AM.I.J.K8 · FAA-H-8083-30B, Ch. 5 (Angle of Attack)

Drill other domains

• Electricity and Electronics (16%)
• Aircraft Drawings (4%)
• Weight and Balance (6%)
• Fluid Lines and Fittings (4%)
• Materials, Hardware and Processes (8%)
• Ground Operations and Servicing (9%)

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