🔍 Key Concepts

• Read the curve carefully at 30% speed (rpm) on the horizontal axis and project up to where it meets the horsepower curve. • Understand that this is a typical propeller load curve, where power changes much faster than speed (roughly with the cube of speed). • Convert between decimal form and percent (e.g., 0.1 = 10%) to compare the graph value with the answer choices.

💭 Think About

• When you go up from 30% on the speed axis to the curve and then left to the % horsepower axis, roughly what percentage does it show? Is it closer to a few percent, tens of percent, or almost zero? • If horsepower varies approximately with the cube of speed, what fraction of power would you expect at 0.3 of full speed? How does that estimate compare with the options? • Look at the point on the curve at 60% speed (where the graph is easier to read) and note the % horsepower there. Does this support the idea that power increases much faster than speed? Use that pattern to judge the 30% point.

✅ Before You Answer

• Be sure you are reading percent horsepower on the vertical axis, not confusing it with speed. • Convert the answer choices from decimals to percent values before comparing to the graph (e.g., 0.04 = 4%). • Double‑check which option best matches the approximate % horsepower you read from the graph at 30% speed, not at 40% or 50%.