9. A river flows with a speed of 0.600 m/s. A student first swims upriver 0.500

Question

9. A river flows with a speed of 0.600 m/s. A student first swims upriver 0.500 km, then turns around and returns to his starting point. The student swims at a constant speed of 1.20 m/s relative to the water. (a) How long does the round trip in the river take? (b) How long would a trip of the same length take in still water? (c) Explain why it takes longer to swim in moving water, considering that it takes longer to swim upriver but shorter to swim downriver tad on ton hile trarelinonstraight track at

Explanation / Answer

As per the question, it's given that student can swim at a speed of 1.2 m/s relative to the still water.

So he can swim (1.2 - 0.6 = 0.6 m/s) in upstream and (1.2 + 0.6 = 1.8 m/s) during downstream.

So upstream at 0.6 m/s, it will take time to cover 0.5 km or 500 metre is find out by -

t = distance / speed

t = 500 / 0.6

t = 833.3 second

t = 13.88 minutes.

During next stream, he will downstream with 1.8 m/s, so the time taken by him is -

t = 500/1.8 = 277.77 second or 4.63 minutes.

A)

So the total time taken by him is sum of the time taken by him in two trips.

T = 833.3 sec + 277.7 sec

T = 1111 sec

T = 18.5 minutes.

B)

So the time taken by him when the water is still is taken out by

t = 1000/ 1.2 = 833.34 sec or 13.88 minutes

C)

If the water is flowing with the same speed as the swimmer can swim (1.2 m/s) then she/he would never get there, time would be infinite. So the faster the stream flow (in either direction) the longer the round trip will take. The shorter the round trip will occur when the water is still.

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