If the piston stroke in a four stroke cycle diesel engine is 10 1/2 inches and the speed of rotation of the crankshaft is 720 RPM, what is the average piston speed?

Correct Answer: Option B — 1260 feet/minute

Average piston speed equals twice the stroke in feet multiplied by the RPM. A 10.5-inch stroke equals 0.875 feet. Multiplying 2 × 0.875 × 720 RPM results in an average piston speed of 1,260 feet per minute.