1. The problem statement, all variables and given/known data A) what force is necessary to maintain 0.5 cm/s flow velocity of blood in the 20 cm long segment of aorta, supposing that the force is needed only to prevail the internal friction. The answer is 11.3 mN, I have no idea what formula to use. The blood viscosity=4.5mPa*s; blood density=1.05g/cm3 B) What percentage intensity increase would cause a turbulent flow? Suppose the flow is stationary. [Pressure=1.6*10^4 Pa] The answer is 24%. Again I have nothing to contribute with here. 2. Relevant equations 3. The attempt at a solution A) I noticed that distance*velocity*viscosity give the right unit, but not answer, so I guess this is just a coincidence. B) Nothing I really have tried a long (!!) time to solve this, so I really hope that someone here can help me! The problem is that I do not have the means to solve it, I have no idea what formula to use or anything. Thank you for your time!