Flight Attendant at Work

Consider a flight attendant pushing a cart forward in a steadily moving plane. There is negligible friction. According to an observer on the plane, the flight attendant does a certain amount of work on the cart, F*d. According to an observer on the ground, the flight attendant does work of F*D, where D>>d. According to the work-energy theorem, the cart has gained a much greater kinetic energy. If we are to use conservation of energy to calculate things, how do we resolve this discrepancy?

a) The observer on the plane is the correct observer.

b) The observer on the ground is the correct observer.

c) Conservation of energy is falsified by this gedanken experiment.

d) Don't worry about it. Conservation of energy holds for both observers.

e) Can't tell

Answer

Last updated January 23, 2007 by Erik Jensen