a worker is poling a boat across a shallow lake. He pushes parallelto the length
ID: 1764491 • Letter: A
Question
a worker is poling a boat across a shallow lake. He pushes parallelto the length of the light pole exerting on the bottom of the lakea force of 235N. Assume the pole lies in the vertical planecontaining the boat's keel. At on moment, the pole makes an angleof 25o with the vertical and the water exerts ahorizontal drag force of 47.5N on the boat opposite to its forwardvelocity of magnitude 0.857 m/s. The mass of the boat including itscargo and the workers is 400kg.a) The water exerts a buoyant force vertically upward on the boat.Find the magnitude of this force.
______ N
b) Model the forces as constant over a short interval of time tofind the velocity of the boat 0.600 seconds after the momentdescribed.
_______m/s
I dont even know how to start this problem
Explanation / Answer
a) We refer to Newton's third law (every action has a reaction of thesame magnitude) then. Fy =m*ax = 400kg * 9.8m/s2 = 3920N However since the pole is exerting force of 235N on the bottom ofthe lake then. 3920N - 235N = 3685N b) We notice that this problem can be solved by kinemtaicsequation Vxf = Vxi+ax*t so Vxi = 0.875m/s t =0.600s ax = ?? we first get ax , so Fx =m*ax ax =Fx / m = 47.5N / 400kg =.1187m/s2 Now we are in business, plug and chug Vx = 0.857m/s + (0.1187)(0.600s) = 0.928
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