A Fitness & exercise forum. FitnessBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » FitnessBanter.com forum » Fitness & Exercise » General
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

the physics of situps



 
 
Thread Tools Display Modes
  #1  
Old December 5th 09, 05:48 AM posted to sci.physics,misc.fitness.misc,rec.martial-arts,alt.martial-arts.karate
Androcles
external usenet poster
 
Posts: 3
Default the physics of situps


"Appledog" wrote in message
...
On Dec 5, 2:39 am, Shuurai wrote:
But Newton's physics tells us an isolated body
cannot generate net momentum; action = reaction.
But I swear I couldn't have completed that segment
without the arm swing. So the question is, did this
trick really work as a cheat, physically? Or was
it just an illusion?


You're shifting your center of gravity.


An isolated body can't shift it's center of gravity.

===================================
Take a straight rod and bend it. The CoG moves from
inside the rod to outside. Engage brain before opening mouth.
Better yet, don't open mouth.



  #2  
Old December 7th 09, 12:17 PM posted to sci.physics,misc.fitness.misc,rec.martial-arts,alt.martial-arts.karate
Androcles
external usenet poster
 
Posts: 3
Default the physics of situps


"Appledog" wrote in message
...
On Dec 5, 12:48 pm, "Androcles" wrote:
"Appledog" wrote in message

...
On Dec 5, 2:39 am, Shuurai wrote:

But Newton's physics tells us an isolated body
cannot generate net momentum; action = reaction.
But I swear I couldn't have completed that segment
without the arm swing. So the question is, did this
trick really work as a cheat, physically? Or was
it just an illusion?


You're shifting your center of gravity.


An isolated body can't shift it's center of gravity.

===================================
Take a straight rod and bend it. The CoG moves from
inside the rod to outside. Engage brain before opening mouth.
Better yet, don't open mouth.


As it's an isolated body, please explain how the center of gravity has
changed location in space, since there was no other body on which to
exert a force.

If what you were really saying were true, then bending over would be a
form of propulsion. It's not in all cases, and you're not getting
anywhere with it either.
=======================================
The only objects referred to in your sentence above are
"a body " and "center of gravity".
"Location in space" is not a reference and you gave no
mention of a location in space when you made your false
claim.

I have pointed out that bending a rod shifts it CoG
(relative to the end points of the rod, although that
should have been obvious).

What I'm really saying is true, and I have not claimed
bending would be a form of propulsion since I have
offered no reference that it would move relatively to
other than the body relative to the centre of gravity or
the centre of gravity relative to the body.





 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
the physics of situps Fraser Johnston[_3_] General 5 August 22nd 14 01:14 AM
the physics of situps Sam Wormley General 1 May 10th 10 08:53 AM
the physics of situps hal General 2 November 15th 09 04:00 AM


All times are GMT +1. The time now is 11:58 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2004-2019 FitnessBanter.com.
The comments are property of their posters.