FAA Aviation Mechanic General (AMG)Physics, Math and Fluid LinesHard
An aluminum tube 10 feet long at 70°F is heated to 220°F. If the coefficient of linear expansion for aluminum is 0.0000131 inch/inch/°F, how much will the tube elongate?
- A0.236 in
- B0.393 in
- C0.118 in
- D1.31 in
Show answer & explanationAnswer & explanation
Correct answer: A. 0.236 in
Length in inches = 10 ft × 12 = 120 in. ΔT = 220 − 70 = 150°F. Elongation = 120 × 0.0000131 × 150 = 0.2358 in, which rounds to 0.236 in.
Why the other options are wrong
- B. This overstates the elongation compared to the correct calculation.
- C. This is roughly half the correct value, suggesting an arithmetic error.
- D. This value is far too large and inconsistent with the coefficient given.
Coefficient of Linear Expansion
A material property describing how much a material's length changes per unit length per degree of temperature change.
- ΔL = L × coefficient × ΔT
- Length must be in consistent units (often inches)
- Different metals have different expansion coefficients
Memory trick: Hot metal stretches — length times rate times rise.