A child walks at 1.5m/s relative to a moving walkway that itself moves 2.0m/s east relative to the airport floor. Three observers measure the child’s speed:
1. The child herself
2. A passenger standing still on the walkway
3. A worker standing on the floor next to the walkway
Which ranking orders the magnitudes of the speeds these observers measure from smallest to largest?
a) 1 < 3 < 2
b) 3 < 1 < 2
c) 1 < 2 < 3
d) 2 < 1 < 3