Sylvia Else il 24/02/2023 07:44:14 ha scritto:
>> For you, are two forces that cancel each other like two forces that are
>> not there?
> If a particle is being pulled in opposite directions by two forces with
> the same magnitude, then the particle will not accelerate.
This is certainly true.
> The effect of the two forces together is the same as no force.
However, this is only partially true.
It is true for the "acceleration" effect but not for the other effects:
compression, stretching, deformation or tension.
Obviously I am referring to the effects on bodies and not to the
effects on particles because nobody knows if the particle compresses or
doesn't compress, if it stretches or doesn't stretch.
>> Check out my simulation
>> In the initial position there are no forces, during the rotation there
>> are and they cancel each other out.
>> They are the same thing? No!
>> Because without rotation (initial position) the body is spherical and
>> the string is not under tension.
>> Instead, during the rotation the body is stretched and the string is
>> under tension.
>> So, in the second case, the forces exist and both act even when they
>> cancel each other out.
> It the forces originating from the stretching of the body that cancel out.
No, it's not the forces that cancel each other out!
I'll give you a clarifying example.
If they push you from the left, they compress where they hit you and
accelerate you to the right.
There is force and there are two effects: compression and acceleration.
If they push you with the same force, both from the right and from the
left, the compression effect is still there, the acceleration effect is
So, forces don't disappear and compression doesn't disappear either,
the only thing that disappears is acceleration.
>> If we put a dynamometer between point B of the string and point C of
>> the body of mass m when there is no rotation, it tells us that there
>> are no forces (and, consequently, there are no tensions and no
>> elongations) .
>> If we put it during a rotation, there are forces, tensions and
>> So the forces are there even when they cancel each other out.
>> They don't disappear.
> Cancelling out doesn't mean that forces disappear,
Exact! Did you see that you recognize him too?
> just that they combine to produce no acceleration.
That's right: it's the acceleration that vanishes, not the forces!
>> The forces generate the rotation which, being a motion, can disappear
>> when the reference is changed.
> The acceleration does not disappear with any change of reference frame,
> provided that the reference frame is inertial.
Acceleration (which is motion) disappears in accelerated references,
not in inertial ones.
But force does not disappear because it is not motion and tension does
not disappear because it is not motion.
>> But do you agree with me that they also generate tension and elongation
>> which, not being motions, do not disappear when the reference is
> The shape in a different reference frame in described by the Lorentz
We are not talking about relativistic speeds here!