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