Re: The "net" force

Mikko il 24/03/2025 10:14:22 ha scritto:

On 2025-03-22 16:31:37 +0000, Luigi Fortunati said:
 

In the animation https://www.geogebra.org/classic/sr8fxezb there is =

the

force F of the hand that pushes the point A of the car.
 
The force F that pushes the car is certainly a "net" force because
there is no one to push the car from the other side.
 
But is the force F that pushes the point A of the car also a "net"
force?

 
A net force to the car is not a net force to a part of the car.

 
I agree: the force F of the hand is a net force on the car but it is
not a net force on point A.
 
Consequentially, on point A there must be *also* a force acting
contrary to the force F.
 
So, does the blue reaction contrary force FR of my animation act only
on the hand that pushes (as you all keep saying) or does it act *also*=

 

on point A of the car?

>
The interactions are between material parts. A point does not interact.

I am referring to the material point, that is, the particle.

Particle A of the machine, in addition to receiving the black force F
of the hand, does it or does it not receive the blue reaction force FR
of my animation?

Luigi

[[Mod. note -- No, it doesn't: the reaction force FR (shown in blue)
acts on the hand, whereas particle A is part of the car.

I should also point out one important error in the diagram: the diagram
shows FR as different in magnitude (arrow of length 2) from F (arrow of
length 3).  Newton's 3rd law says that FR has the same magnitude as F,
so these two arrows should be shown as the same length.
-- jt]]