A swimmer is capable of swimming 1.05 m/sin still water. (a) If she aims her bod

Question

A swimmer is capable of swimming 1.05 m/sin still water. (a) If she aims her body directly across a150-m-wide river whose current is 0.75m/s, how far downstream (from a point opposite her starting point)will she land?
1 m

(b) How long will it take her to reach the other side?
2 s

and

The cliff divers of Acapulco push off horizontally from rockplatforms about h = 28 m abovethe water, but they must clear rocky outcrops at water level thatextend out into the water d = 4.6m from the base of the cliff directly under their launch point. Seethe figure. What minimum pushoff speed is necessary to clear therocks?
1 m/s

How long are they in the air?
2 s
(a) If she aims her body directly across a150-m-wide river whose current is 0.75m/s, how far downstream (from a point opposite her starting point)will she land?
1 m

(b) How long will it take her to reach the other side?
2 s

and

The cliff divers of Acapulco push off horizontally from rockplatforms about h = 28 m abovethe water, but they must clear rocky outcrops at water level thatextend out into the water d = 4.6m from the base of the cliff directly under their launch point. Seethe figure. What minimum pushoff speed is necessary to clear therocks?
1 m/s

How long are they in the air?
2 s

Explanation / Answer

The time it will take her to swim across is .       time = dist /speed = 150 / 1.05 =   142.86 seconds .     the river will pull her a distanceof      dist = speed * time = 0.75 *142.86 =   107.1 meters downstream .      it will take her   143 seconds to reachthe other side . they are in the air for a timeof      t = ( 2 h / g)1/2 =  (2*28 / 9.8)1/2 = 2.39 seconds .    so they need an initial horiz speedof     speed = dist / time = 4.6 /2.39 =    1.92m/s .        time in air  = 2.39 seconds

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