A small propeller airplane flies due north at a constant speed of 50 m/s relative to a stretch of level ground. Inside the airplane cabin, a flight attendant walks south (toward the tail) at 2 m/s relative to the airplane aisle. Meanwhile, a weather balloon drifts due north at 8 m/s relative to Earth along the same straight north–south line.
Assume that vertical motion and wind effects other than the stated balloon drift are negligible.
(a) For each of the following observers, indicate whether the flight attendant is seen moving north, south, or remaining at rest. Justify each choice qualitatively.
(1) A meteorologist tracking the balloon from the ground
(2) The pilot of the airplane
(3) A scientist riding inside the weather balloon
(b) Rank, from greatest to least, the magnitude of the flight attendant’s velocity as measured by the three observers in part (a). State and explain any equalities.
(c) Without performing explicit calculations, explain which, if any, observer(s) in part (a) measure(s) the greatest magnitude for the airplane’s velocity. Use coherent qualitative reasoning tied to reference-frame concepts.