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A boat, whose speed in still water is 1.96 m/s, must cross a W = 217 m wide river and arrive at a point D = 111 m upstream from where it starts, as shown in figure below.



To do so, the pilot must head the boat at a 42.9° upstream angle. What is the speed of the river's current?

Verified Answer :

syed514

if u resolve the inital velocity

then u will get the vertical component to be 1.96cos 42.9

= 0.732 1.96=1.434 m / s

time taken to cross = 217 / 1.434=151.32seconds

distance travelled in x direction = 111m

initial velocity in x direction = - 1.96 sin 42.9 =
= -0.680 1.96= - 1.33

disance = speed time

d = (v of current + velocity of man) time
111= (v - 1.33)* 151.32

v - 1.33 = 0.733
v= 1.33 + 0.73 = 2.063