scenario - A free falling body impacts water at terminal velocity. During what time period is the body considered to be in impact. I am trying to calculate the impact force alone. Is the impact force considered at the initial contact, during the body is fully transitioning from one medium to the next (air to water) complete submertion.. or is the impact force considered over a time period from initial contact up to when ones body is descending due to a negative (neutral) bouyancy alone?? I know alot of forces are involved.. air drag.. surface tension.. parasitic drag..turbulance.. bouyancy forces.. gravity. really what is the deffinition of the impact force in this scenario and how do I calculate it??