Question

two passengers are on a moving sidewalk at the airport. Passenger A is standing still while passenger B is walking with a speed of 2.0 km/h. The sidewalk is moving west at a speed of 1.5km/h. What is the speed of passenger B relative to an observer standing nearby.

Answer 1

The speed of passenger B relative to an observer standing nearby is 0.5 km/h.

Step-by-step explanation:

The speed of passenger B relative to an observer standing nearby can be calculated by taking the difference between the speed of passenger B and the speed of the moving sidewalk. In this case, passenger B is walking with a speed of 2.0 km/h and the sidewalk is moving west at a speed of 1.5 km/h. So the speed of passenger B relative to the observer will be 2.0 km/h - 1.5 km/h = 0.5 km/h.

Answer 2

A thing the question doesn't tell us: What direction is Mr. B walking ?

-- If Passenger B is walking West, in the same direction as the moving walkway, then the stationary observer sees him passing by toward the West at 3.5 km/hr.

-- If Passenger B, for some strange reason, is walking BACKWARDS, heading east on the moving walkway, then the stationary observer sees him passing by toward the EAST, at 0.5 Km/hr.

-- We're wondering why the question ever introduced us to Passenger-A. He never figures into the question in any way. He has no effect on Passenger-B, and we never hear from him again.