# Free Fall and air resistance

1. Feb 5, 2008

### hydrogen

Hey guys,

when an object is free falling, is it still under the effects of air resistance? If it was not under the effects (an environment with out air resistance) is free fall possible? (I am looking for an argument that it is under the effects of free fall but all replies will be taken into consideration)

2. Feb 5, 2008

### rock.freak667

When a body is falling through the air there are three forces acting on it, Weight(W), Friction(F) and upthrust(U).
The resultant force is given by $F_R=W-U-F$, when in free fall the resultant force is zero. So then the air resistance is still there but the weight is numerically equal to the sum of the air resistance and upthrust.

3. Feb 5, 2008

### Andy Resnick

If someone is free-falling off a bridge, there is air resistance. Geosynchronous satellites are in free-fall, and there is no air resistance.

Sounds like a discussion about a definition rather than physics?

4. Feb 5, 2008

### Staff: Mentor

Yes, it is a discussion about a definition. The technical physics definition is falling where the only force acting on you is gravity. So that means jumping out of a plane doesn't qualify. But definitions are a matter of consensus, so the dictionary has that one in there too.