Undergrad Do action force and reaction force lie on same line?

[fxdung]

Do action force and reaction force(Newton's third law) lie on same line?If not then the angular momentum will be violated.I don't know why a cat falling can rotate itself before contact land if the conservative law of angular momentum not be violated?

 

[fxdung]

I know that the conservative law of angular momentum is deduced from the symmetry of rotation of space.So the torque of internal force must be zero,then the action and reaction forces must be lie in same axis.But how to prove action and reaction forces lie in same axis(it seem to me sometime the action and reaction forces not lie on same axis)?

 

[hutchphd]

Do action force and reaction force(Newton's third law) lie on same line?If not then the angular momentum will be violated.I don't know why a cat falling can rotate itself before contact land if the conservative law of angular momentum not be violated?

The short answer is the cat is not a rigid body. Newtons Laws are inviolate and there are no external torques on the cat but by clever counterotation the cat can get her feet downward without offending Sir isaac.

https://www.huffpost.com/entry/why-cats-always-land-on-their-feet_n_1828748

 

[rcgldr]

Conservation of angular momentum doesn't mean that angular orientation can't be changed due to internal torques. If you were standing on a frictionless surface, you could whirl your arms overhead to change the direction you face. A cat flexes at the middle and whirls it's front half and back half in order to change orientation to face paws down.

 

[A.T.]

I don't know why a cat falling can rotate itself before contact land if the conservative law of angular momentum not be violated?