🔍 Key Concepts

• Indicated horsepower (IHP) formula for reciprocating engines: IHP = PLAN/33,000 • Meaning of each term: P (mean effective pressure), L (stroke length), A (piston area), N and how it relates to time and engine cycle • Difference between power strokes and revolutions in 2‑stroke vs 4‑stroke engines

💭 Think About

• Think about whether the formula needs a value "per minute" or "per revolution" to end up with horsepower, which is power over time • Consider how many power strokes occur for each revolution in a 2‑stroke engine versus a 4‑stroke engine • Ask whether N should change for 2‑stroke vs 4‑stroke engines, or stay as a common measure for both

✅ Before You Answer

• Check that the units of PLAN divided by 33,000 work out to horsepower (hp), which is ft‑lb per minute • Verify whether N must represent something that is directly in "per minute" to match horsepower units • Confirm how the number of power strokes relates to engine speed (RPM) for 2‑stroke and 4‑stroke engines before choosing among the options