Part A Mary needs to row her boat acros8 8 180 1 -wide river that s flowing to t

Question

Part A Mary needs to row her boat acros8 8 180 1 -wide river that s flowing to the east at a speed of 1.1 m/8.Mary can row with a speed of 3.2 m/s If Mary points her boat due north how tar from her intended landing spot will she be when she reaches e oppoie shore? Express your answer using two significant figures meters east (downstream) from where she intended. Submit Reauest Answe Part B What is her speed with respect to the shore? Express your answer to two significant figures and include the appropriate units. Value Units Submit Request Answer

Explanation / Answer

(A)

If she rows directly North or South, her speed relative to shore will be the vector sum of her speed relative to the water and the waters speed relative to shore

v = (3.2² + 1.1²)

v = 3.38 m/s

She will cross the stream in a time of

t = d/v = 180 / 3.2 = 56.25 s

and will end up

1.1(56.25) = 62 m downstream from the point where she started.

(B) If she angles her boat upstream so that her path across the stream is the shortest distance from her starting point to a point on the opposite shore

then

the angle she must row will have an upstream component of her total speed relative to water equal to the stream's speed relative to ground.

sin = 1.1 / 3.2

= 20.1°

so her speed relative to ground will be

v = 3.2cos20.2 = 3 m/s

and it will take her

180 / 3 = 60. s

to row across

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