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River Problems
Swimming upstream or downstream(assume that the swimmer can swim at 2 m/s in still water)
0.5 m/s
VSG= 2 + 0.5 = 2.5 m/s
VSG= 2 – 0.5 = 1.5 m/s
S: SwimmerW: WaterG: Ground
Crossing the River(and “WANTING” to go straight across)
D’ OH!
Crossing the River(assume that the swimmer can swim at 4 m/s in still water)
3 m/s
4 m/s
4 m/s
3 m/s 3 m/s
5 m/s
2.65 m/s
The water speeds the swimmer up …. BUT, he lands downstream
The water slows him down … BUT, he goes straight across
Crossing the River(assume that the swimmer can swim at 4 m/s in still water)
3 m/s
4 m/s
3 m/s
5 m/s
USE 60 = 4t to find the time needed to cross the river. 15 sec
USE d = 3(15) to find the distance the man travels downstream.45 m
60 m
Crossing the River(assume that the swimmer can swim at 4 m/s in still water)
3 m/s
4 m/s
3 m/s
5 m/s
S: SwimmerW: WaterG: Ground
VSW = 4 m/s [A]VWG = 3 m/s [DS]VSG = 5 m/s [DS 53o A]
53o
A
US DS
Crossing the River(assume that the swimmer can swim at 4 m/s in still water)
4 m/s
3 m/s
2.65 m/s
USE 60 = 2.65t to find the time needed to cross the river.
t= 22.64 sec (slow, but straight)
60 m
Crossing the River(assume that the swimmer can swim at 4 m/s in still water)
4 m/s
3 m/s
2.65 m/s
S: SwimmerW: WaterG: Ground
VSW = 4 m/s [US 41.5o A]VWG = 3 m/s [DS]VSG = 2.65 m/s [A]
41.5o
A
US DS