I did the problem, got the correct answer but dont' know why I was supposed to do it this way! Please help me understand the reasoning behind all this:(adsbygoogle = window.adsbygoogle || []).push({});

A swimming is capable of swimming .45m/s in still water. She is swimming across a 75 m wide river whose current is .40 m/s. A) at what upstream angle must the swimmer aim if she is to arrive at a poitn directly across the stream? B) How long would it take her?

I drew a picture and set the x and y components separately. So V being velocity, WL = water with respect to Land, SL swimmer respect to land, and SW swimmer respect to water .. I got

Vwlx= 0 Vslx = ? Vswx = ?

Vwly = .4 Vsly = 0 Vswy = ?

A) to find the angle I took the inverse sin of .40/.45 to get 62.74 . However doesn't this depend on the picture? The way my profesor explained it, he drew it so that it would be inverse cos .. BEcause this confused me I drew it differently so that inverse sin would make sense. According to the drawing, the answer shouldn't be different but then why does it seem like it should be?

B) then I took Vswy = VwLy + VsLy to get

Vswy = .40 + 0 = .4 < this I understand

.4 = .45sin(angle) << this I do not. Why do we set this up this way?

Inv sin (.4/.45) =angle

62.74 degrees ..

then to get the x component <<again, I don't understand why we set this up this way.

Vswx = .45cos(62.74)

Vswx = .206

distance formula:

D=VT

75= .206t

75/.206 = t

t= 363.8 s

Any help would be appreciated.

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# Homework Help: Solved it; Don't understand it.

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