Question
A dolphin wants to swim directly back to its home bay, which is 0.800 km due west. It can swim at a speed of 3.58 m/s relative to the water, but a uniform water current flows with speed 2.95 m/s in the southeast direction.
Answers
bobpursley
draw the diagram. t is time swimming
2.95*t*sin135S + 2.95tcos(135)E+3.58tSinTheta N+3.56tCosTheta W = 800W
Now looking at NS only
2.95*t*sin135S +3.58tSinTheta N=0
t divides out, so
Theta= arcsin 2.95/3.58= 180+55.5 deg, that is the direction he has to swim. Now, how long? Look in the EW direction.
2.95tcos(135)E+ 3.56tCosTheta W = 800W
time=800/(2.95 cos(135) - 3.56 Cos55.5)=11317 sec which is a long time.
check my math.
2.95*t*sin135S + 2.95tcos(135)E+3.58tSinTheta N+3.56tCosTheta W = 800W
Now looking at NS only
2.95*t*sin135S +3.58tSinTheta N=0
t divides out, so
Theta= arcsin 2.95/3.58= 180+55.5 deg, that is the direction he has to swim. Now, how long? Look in the EW direction.
2.95tcos(135)E+ 3.56tCosTheta W = 800W
time=800/(2.95 cos(135) - 3.56 Cos55.5)=11317 sec which is a long time.
check my math.
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