1. The problem statement, all variables and given/known data Humans have about v = 60 cm3 of blood per kilogram of body mass and blood makes a complete circuit in t = 20 s seconds. For a human body of thickness 0.2 m and height 1.8 m, estimate the change in power output of the heart when the body is standing up on a horizontal surface compared to when the body is lying down on the same surface. Assume that the density of blood is ρ = 0.001 kg/cm3 and the mass of the human body is 66 kg. Use g = 9.8 m/s 2. Relevant equations P = W/t Conservation of energy 3. The attempt at a solution Completely clueless really. I assume that I need to use conservation of energy to find the work. I set mgh as the PE of the body for both cases when h = 1.8 (standing horizontal) and h=0.3 (lying down) however, I have no idea how I could find the work that the blood does. Can anyone explain to me how I can go about doing that?