FAA Aviation Mechanic General (AMG)Physics, Math and Fluid LinesHard
A 5-pound aluminum engine component (specific heat 0.214 BTU/lb°F) is heated in an oven from 70°F to 220°F for a stress-relief process. How much heat energy, in BTU, is absorbed by the component?
- A160.5 BTU
- B16.05 BTU
- C321.0 BTU
- D1,605 BTU
Show answer & explanationAnswer & explanation
Correct answer: A. 160.5 BTU
Heat energy is found with Q = m × c × ΔT. ΔT = 220°F − 70°F = 150°F. Q = 5 lb × 0.214 BTU/lb°F × 150°F = 160.5 BTU.
Why the other options are wrong
- B. This results from using a temperature change of 15°F instead of 150°F.
- C. This value comes from doubling the correct answer in error.
- D. This results from using a temperature change of 1,500°F instead of 150°F.
Specific Heat / Heat Energy Formula
The heat energy required to change a material's temperature is found using Q = mass × specific heat × temperature change.
- Q = m × c × ΔT
- Specific heat (c) is unique to each material, measured in BTU/lb°F
- ΔT must be the actual temperature change, not the final temperature alone
Memory trick: 'Mass meets heat capacity times the change' to find the BTU total.