A swimmer is able to swim at a speed of 0.89 m/s in still water. (a) How long do

Question

A swimmer is able to swim at a speed of 0.89 m/s in still water.

(a) How long does it take the swimmer to go a distance of 1650 m in still water? Call this time t1.
t1 =  s

(b) The swimmer then decides to swim the same distance in a river having a current with a speed of 0.55 m/s. How long does this take if she swims with the current? Call this time t2.
t2 =  s

(c) How long does it take her to swim the same distance against the current? Call this time t3.
t3 =  s

(d) Explain why t1 t2 is not equal to t3 t1.

t1 t2 is not equal to t3 t1 because the upstream swim takes around 4 times longer than the downstream swim.t1 t2 is not equal to t3 t1 because the distance is constant.    t1 t2 is not equal to t3 t1 because times are added straightforwardly.

Explanation / Answer

a)

Vs = speed of swimmer in still water = 0.89 m/s

d = distance travelled = 1650 m

t1 = d/Vs = 1650/0.89 = 1853.93 sec

b)

Speed of current = 0.55 m/s

Net speed of swimmer = Vs' = Vs + 0.55 = 0.89 + 0.55 = 1.44 m/s

d = distance travelled = 1650 m

t2 = d/Vs' = 1650 / 1.44 = 1145.83 sec

c)

Speed of current = 0.55 m/s

Net speed of swimmer = Vs'' = Vs - 0.55 = 0.89 - 0.55 = 0.34 m/s

d = distance travelled = 1650 m

t3 = d/Vs'' = 1650 / 0.34 = 4852.94 sec

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