A moving sidewalk has a velocity of 1.5 m/s north. If a man walks south on the sidewalk at a speed of 0.8 m/s, how long does it take him to travel 10 m
relative to a stationary observer?
A. 14.3 s
O B. 12.4 s
C. 6.7 s
D. 9.5 s

Awater slide of length l has a vertical drop of h. abby's mass is m. an average friction force of magnitude f opposes her motion. she starts down the slide at initial speed vi. use work-energy ideas to develop an expression for her speed at the bottom of the slide. then evaluate your result using unit analysis and limiting case analysis. express your answer in terms of the variables h, m, l, vi, f and appropriate constants. vf v f