Free Fall vs. Not Free Fall?

In summary, an object falls with friction, and contact compression interaction is when air is compressed by the object.
  • #1
eraemia
53
0
Hello,

If free fall is defined as falling with the absence of friction, then what interactions does an object participate in if it falls with friction? The first obvious answer is that the object participates in a contact friction interaction with the air (or air friction). The second answer is a long-range gravitational interaction, which pulls the falling object toward the center of the earth.

But what other interactions are at play? For example, if air is matter, and if the falling object contacts air, therefore compressing it, could we call this a contact compression interaction, where the air is pushing the object in whatever opposite direction the object is pushing the air? What really is air friction? A contact friction or contact compression interaction? If there is indeed a contact compression interaction with the air, how does this interaction affect the motion of the falling object, and how does it differ from the contact friction's effect on the falling object?

Thanks for the help.
 
Physics news on Phys.org
  • #2
The complete answer can be quite complicated - here are some parts.

1. There is a friction effect (aerodynamicists describe it in terms of boundary layers).
2. There is a general flow effect - the air has to go around the object.
3. Turbulence leads to a drastic lowering of pressure behind the object, so there is slowing resulting from front to back pressure difference.
4. At supersonic speeds, there is a compression effect (sonic boom).

All the above are relevant for any object going through a fluid (air or water), not just falling.
 
  • #3
I thought that free fall was when the acceleration downward (towards the Earth) was equal to the Earth's acceleration due to gravity 9.81 m/s. Friction due to drag effects the terminal velocity due to a host of other variables, such as surface area. So I am a bit confused as to what u are asking with contact friction and compression interaction, how do they differ in this case?
 
  • #4
Thanks mathman, though that sounds beyond my level of physics atm...

I'm just as confused as you, t-money. I'm not even sure if both interactions occur, and if they, what their difference is.
 

What is the difference between Free Fall and Not Free Fall?

Free Fall is a motion where an object falls towards the ground under the influence of gravity only, with no other forces acting on it. Not Free Fall, on the other hand, is any motion where other forces besides gravity are acting on the object.

How does the speed of an object in Free Fall change?

The speed of an object in Free Fall increases at a constant rate of 9.8 meters per second squared, due to the acceleration of gravity. This means that the object will fall faster and faster until it reaches terminal velocity or hits the ground.

What is terminal velocity?

Terminal velocity is the maximum speed that an object can reach while falling through a fluid, such as air or water. It occurs when the force of gravity pulling the object down is equal to the force of air resistance pushing against the object.

How does air resistance affect Free Fall?

Air resistance, also known as drag, is a force that opposes the motion of an object through a fluid. In Free Fall, air resistance increases as the object falls faster, until it reaches terminal velocity. This is why objects with different surface areas or shapes will have different terminal velocities.

Can an object experience both Free Fall and Not Free Fall at the same time?

Yes, an object can experience both Free Fall and Not Free Fall at the same time. For example, a skydiver in Free Fall is also experiencing air resistance, making it Not Free Fall. However, once they deploy their parachute, the air resistance increases and becomes the dominant force, causing the skydiver to no longer be in Free Fall but rather Not Free Fall.

Similar threads

  • Mechanics
Replies
3
Views
853
Replies
3
Views
876
Replies
12
Views
4K
  • Mechanics
Replies
2
Views
1K
Replies
16
Views
2K
  • Mechanics
Replies
11
Views
1K
  • Mechanics
Replies
10
Views
1K
Replies
12
Views
864
Replies
30
Views
4K
Back
Top