FAA Aviation Mechanic General (AMG)Physics, Math and Fluid LinesMedium
A sample of hydraulic fluid weighs 7.3 pounds per gallon. Water weighs 8.34 pounds per gallon at the same temperature. What is the specific gravity of the hydraulic fluid?
- A0.73
- B1.14
- C0.875
- D8.34
Show answer & explanationAnswer & explanation
Correct answer: C. 0.875
Specific gravity is the ratio of a substance's density to the density of water. Specific gravity = 7.3 ÷ 8.34 = 0.875.
Why the other options are wrong
- A. This value does not match the correct division.
- B. This results from inverting the ratio (water ÷ fluid).
- D. This is simply the weight of water, not a ratio.
Specific Gravity
The ratio of the density (or weight) of a substance to the density of water at the same temperature.
- Specific gravity = substance weight ÷ water weight
- Water has a specific gravity of 1.0
- Values below 1.0 indicate the substance is lighter than water
Memory trick: Compare everything to water's baseline of 1.0.