# Hudson River accident. Friction on water

1. Jan 28, 2013

### MikeyMike

1. The problem statement, all variables and given/known data
I am in an introductory physics course. I am an aviation student, and we have to present on something related to our major. My group decided to go with an analysis on the Hudson River incident.

I am trying to figure out the force of friction the water had on the aircraft. What I do have
1) Airbus A320 Max Takeoff weight is 73500kg. The aircraft incident was only a few minutes after takeoff so we can use this number
2) The speed of the aircraft right before contact with the water is about 67 meters per second.
3) The aircraft moved along the water for about 5 seconds before coming to a complete stop. If my math was correct, this gave the aircraft an acceleration of about -13.4m/s^2 Southbound
(The distance traveled across the water is unknown)

2. Relevant equations
This is one of the problems I am having. I can only find equations and friction properties for solid on solid. This is where I need help.

3. The attempt at a solution
My attempt at the solution is what was posted above. Again, were going ahead of ourselves with this one and I'm hoping one of you can at least point me in the right direction.

2. Jan 28, 2013

### szimmy

The resistive force that water exerts is called drag, not friction. Friction occurs between two solid objects, and water being a liquid, behaves differently. You would be able to calculate the resistive force that water put on the plane, but there isn't a coefficient of friction to find.

3. Jan 28, 2013

### haruspex

Confusingly, drag on the surface of a liquid is sometimes called 'skin friction' (http://en.wikipedia.org/wiki/Parasitic_drag#Skin_friction).
The principal difference between that and solid-solid friction is that the latter is (generally) taken to be independent of speed, whereas drag/skin friction almost surely is not.