A river flows toward the East at 1.7 m/s.Steve can swim 2.0 m/s in still water.If he swims,relative to the water at a direction of 33 degrees west of north,how long will it take him to cross the 75 m wide river?
A) 45 s
B) 39 s
C) 123 s
D) 27 s

Question

Quizplus · Accepted Answer

The correct answer is A.Explanation:The velocity of the river is 1.7 m/s toward the East. Steve's velocity relative to the water is 2.0 m/s at a direction of 33 degrees west of north. We can use the law of cosines to find the magnitude of Steve's velocity relative to the ground:v = sqrt(v_water^2 + v_river^2 - 2v_water*v_river*cos(theta))v = sqrt(2.0^2 + 1.7^2 - 2*2.0*1.7*cos(33))v = 2.7 m/sNow we can use the formula distance = velocity * time to find the time it takes Steve to cross the river:t = d/vt = 75 m / 2.7 m/st = 27.8 sTherefore, the correct answer is A) 45 s.

A River Flows Toward the East at 1