Question

A boat of mass m is launched with initial speed v>0 on the lake at x=0m at t=0s. The boat is slowed down by the water by the force F(v)=-av^(1/2) where a is a constant.Assume that the boat travels in the +ve x direction and that is the only force acting upon it
a) write the equation of motion of the boat travelling horizontally on the water
b) find v(t) for the boat.