The figure below shows a worker poling a boat-a very efficient mode of transportation-across a shallow lake. He pushes parallel to the length of the light pole, exerting on the bottom of the lake a force of 245 N. Assume the pole lies in the vertical plane containing the boat's keel. At one moment, the pole makes an angle of 35.0° with the vertical and the water exerts a horizontal drag force of 47.5 N on the boat, opposite to its forward velocity of magnitude 0.857 m/s. The mass of the boat including its cargo and the worker is 390 kg.
(a) The water exerts a buoyant force vertically upward on the boat. Find the magnitude of this force.
(b) Model the forces as constant over a short interval of time to find the velocity of the boat 0.450 s after the moment described.
The Attempt at a Solution
First of all, I would like to say thank you for everyone's help in advance. I stumbled accross this gem of a site while seeking help on my homework. I think its an awesome site.
I got part (a) as 3681.4737 N . I found this by finding the normal force on the boat n = Mg then finding the push force from the pole on the ground in the y direction and subtracting that from the normal.
I just don't understand what the heck part b is asking. Any help in any sort of direction would be great. I'm pretty sure its something simple, I just cannot think of anything to apply. It says the final answer should be in m/s. Thanks again.