FAA Aviation Mechanic General (AMG)Physics, Math and Fluid LinesHard
A mechanic uses a hoist to lift a 550-pound engine component a vertical distance of 10 feet in 20 seconds. How much horsepower is required to perform this work (1 hp = 550 ft-lb/sec)?
- A5.0 hp
- B10.0 hp
- C1.0 hp
- D0.5 hp
Show answer & explanationAnswer & explanation
Correct answer: D. 0.5 hp
Work = Force × Distance = 550 lb × 10 ft = 5,500 ft-lb. Power = Work ÷ Time = 5,500 ft-lb ÷ 20 sec = 275 ft-lb/sec. Horsepower = 275 ÷ 550 = 0.5 hp.
Why the other options are wrong
- A. Overstates power by a factor of 10.
- B. Overstates power by a factor of 20.
- C. Results from an error in the time calculation.
Work, Power, and Horsepower
Work equals force times distance; power is the rate at which work is done, often expressed in horsepower.
- Work = Force × Distance (ft-lb)
- Power = Work ÷ Time (ft-lb/sec)
- 1 horsepower = 550 ft-lb/sec
- Faster work performed for the same task requires greater power
Memory trick: Work is the job, power is how fast you finish it.