Re: Confusion redux: "Centrifugal Force"


Paul B. Andersen wrote:
Mike wrote:
Paul B. Andersen wrote:
Mike wrote:
Tom Roberts wrote:
Mike wrote:
Tom Roberts wrote:
When I whirl a stone on a string around my head, the centripetal force
is the inward force of string tension on the stone, and the reaction to
the centripetal force is the outward force of string tension on my hand.
I would like to inform you that this force is what we call a
centrifugal force.
That's your problem right there -- this most definitely is NOT
"centrifugal force". This is a force of TENSION IN THE STRING. The
"centrifugal force" acts ON THE STONE, not on my hand. <shrug>
if you have both the centrifugal force and the centripetal force acting
on the stone then the stone does not move. In the inertial reference
frame, the centrifugal force acts on the hand and IT IS the tension on
the spring and that is why it is measurable.
There is but one force acting on the stone, and that is
the centripetal force acting towards the centre.
That is why the stone is accelerating towards the centre!
F = ma, F and a are vectors.

In the rotating frame, a force must be added to the stone to explain
the apparent motion. This JUST happens to be equal to the reaction
force, the centrifugal force.
In the rotating frame, the stone is NOT moving despite the fact
that a centripetal force is acting on it. That's why a pseudo force
must be added to the stone to explain the apparent LACK of motion.

You must review your mechanics dusted notes.

For an observer on a rotating table there is a measured force on the
ball or stone but he does not see any motion. Thus the observer
includes that besided the force measured by the spring there must be
another, equal and opposite force acting on the ball. Now, get this
well in your mind or review you notes:

- the force acting on the spring is the centrifugal force and it
extends it.

No, it is the reaction force to the centripetal force that
is extending the spring.

All you problems start from the above statement.

Both statements below are dynamically equivalent for the purpose of
analyis and result in consistent analysis:

(A) the centripetal force is the reaction to the centrifugal force

(B) the centrifugal force is the reaction to the centripetal foce

But the force on the spring is the centrifugal fforce, the force that
tries to make the spring "fugal" from the "centri" of the rotation.
This is the force that the srping measures naturally. The centripetal
force is the force on the stone.

Now you are trying hard to deny that a force measured by a sping is a
REAL force.

Get REAL. Stop spewing crap. Your red herring about what causes what is
just that: Whether action or reaction it is damn REAL.

Mike

.

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