Answer
(a) It will take 14 seconds when walking in the same direction as the moving sidewalk.
(b) It will take 70 seconds when walking in the opposite direction as the moving sidewalk.
Work Step by Step
(a) walking in the same direction:
$v = 1.5~m/s + 1.0~m/s = 2.5 ~m/s$
$t = \frac{x}{v} = \frac{35.0~m}{2.5~m/s} = 14~s$
It will take 14 seconds when walking in the same direction as the moving sidewalk.
(b) walking in the opposite direction:
$v = 1.5~m/s - 1.0~m/s = 0.5 ~m/s$
$t = \frac{x}{v} = \frac{35.0~m}{0.5~m/s} = 70~s$
It will take 70 seconds when walking in the opposite direction as the moving sidewalk.
