A moving sidewalk has a velocity of 1.3 m/s north. If a man walks south on the sidewalk at a speed of 0.9 m/s, how long does it take him to travel 20 m
relative to a stationary observer?
O A. 21.9 s
O B. 15.4 s
O C. 33.3 s
O D. 50.0 s

Please please help!!!

According to social exchange theory, altruistic behaviors benefit the individual who performs them.

This is important 1. what happens to the speed of molecules in water vapor when it condenses to form a liquid? (2 points) the molecules slow down. the molecules speed up. the molecules slow down and then speed up. the molecules speed up and then slow down. 2. how might human activities change to compensate for a decrease in water supplies? (2 points) humans might build a factory. humans might build drainage systems. humans might extract more water from the ground. human behavior does not change because of the water cycle. i'll be grateful if anyone can answer these 2 questions !

In which of the following is positive work done by a person on a suitcase