Physics
posted by Anonymous .
Two canoeists in identical canoes exert the same effort paddling and hence maintain the same speed relative to the water. One paddles directly upstream (and moves upstream), whereas the other paddles directly downstream. With downstream as the positive direction, an observer on shore determines the velocities of the two canoes to be
−1.7 m/s
and +2.5 m/s, respectively.
(a) What is the speed of the water relative to the shore?
m/s
(b) What is the speed of each canoe relative to the water?
m/s

The driver of a speeding empty truck (initial speed of Vi) slams on the brakes and skids to a stop through a distance d. Assuming that the brakes always supply the same stopping force, consider the following situations:
1
(a) If the truck carried a load that doubled its mass, what would be the
truck’s “skidding distance” in terms of d?
2d
d
d/2
d/4
2
(b) If the initial speed (with its initial mass) of the truck were halved, what would be the truck’s “skidding distance” in terms of d?
2d
d
d/2
d/4
3
(c) If the stopping distance is now 4d, what is the initial velocity (Vi) of the truck?
2Vi
Vi
Vi/2
Vi/4 
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