# The motion of cats and stuff in free fall

• Classical
• etotheipi
In summary, the conversation discusses finding resources for learning about continuum mechanics and specifically about mapping between motions in different spaces. The conversation mentions a book by Brannon and a chapter on deformable media that includes a discussion of rigid motion and phantom body forces. The speaker also mentions some personal experiments and notes they will have to put their interest in modeling animals in free-fall on hold due to other responsibilities.
etotheipi
Hey everyone, where can I learn fairly rigorousoly about continuum mechanics and specifically about how to map between motions in the configuration space ##\mathcal{C}## and motions in the shape space ##\mathcal{C} / SO(3)##? I would like to model the general motion of deformable bodies with constant angular momentum about the mass centre, thanks!

From the publishers site

Frontmatter
https://iopscience.iop.org/chapter/978-0-7503-1454-1/bk978-0-7503-1454-1ch0.pdf

Introduction
https://iopscience.iop.org/chapter/978-0-7503-1454-1/bk978-0-7503-1454-1ch1.pdf

The rest are behind a paywall.

Check out the description of Chap 24
“Chapter 24 returns to the problem of deformable media, but considers the case that bulk rigid motion is the primary motion, with relatively small deformations with respect to an appropriately defined rigidly moving observer frame (e.g., turbine blade, human bodies in a braking automobile, etc). Phantom body forces are derived to allow solving the problem in a non-inertial material frame.”

24 Pseudo-body force for spinning problems 24-1
24.1 Kinematics of superimposed rotation (general analysis) 24-1
24.2 Fiducial body force for superimposed rigid motion 24-7
24.2.1 Special case: pure accelerated translation 24-8 (without rotation)
24.2.2 Special case: centrifuge (steady rotation 24-9 without translation)
24.2.3 Buried explosives 24-11
Reference 24-12

Sounds like your cat dropping experiment.

Last edited:
etotheipi
I did also find some notes here, which at a glance look alright:
https://web.mit.edu/abeyaratne/Volumes/RCA_Vol_II.pdf

not sure if there's anything about spinny cats in them, though! I'm afraid, I'm probably going to have to put the whole modelling various animals in free-fall thing on hold for the moment, because I have write-ups due tomorrow

vanhees71 and Frabjous

## 1. How do cats and other objects behave in free fall?

In free fall, cats and other objects will experience the same acceleration due to gravity, causing them to fall at the same rate. This means that they will appear to be weightless and will not experience any resistance from the air.

## 2. Why do cats always land on their feet when falling?

Cats have a natural instinct to orient themselves in a certain way when falling, known as the "righting reflex". This allows them to twist their bodies mid-air and land on their feet, reducing the impact of the fall.

## 3. Is there a limit to how fast a cat can fall?

Yes, all objects, including cats, have a terminal velocity when falling due to air resistance. This means that they will eventually reach a maximum speed and will not accelerate any further.

## 4. Can cats survive a fall from any height?

Cats have a better chance of surviving a fall from a higher height due to their ability to spread out their body and slow down their descent. However, there is no guarantee of survival and it ultimately depends on the individual cat and the surface they land on.

## 5. How does the weight of a cat affect its motion in free fall?

The weight of a cat does not affect its motion in free fall. All objects, regardless of their weight, will fall at the same rate in a vacuum. However, in the presence of air resistance, a heavier cat may have a slightly higher terminal velocity due to its increased mass.

### Similar threads

• Special and General Relativity
Replies
5
Views
1K
• Science and Math Textbooks
Replies
6
Views
8K
• Mechanics
Replies
13
Views
2K
• Classical Physics
Replies
86
Views
4K
• Mechanical Engineering
Replies
8
Views
1K
• Mechanics
Replies
3
Views
931
• Classical Physics
Replies
7
Views
1K
• Special and General Relativity
Replies
30
Views
3K
• Mechanics
Replies
1
Views
1K
• Special and General Relativity
Replies
10
Views
2K