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WHY do some people try and deny the existence of Centrifugal force ?

WHY do some people try and deny the existence of Centrifugal force ? - Physics Forum

WHY do some people try and deny the existence of Centrifugal force ? - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


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  #1  
Old 07-21-2004, 07:44 PM
sam1967@hetnet.nl
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Default WHY do some people try and deny the existence of Centrifugal force ?



why ????????????

my schoolteacher and unicersity lecturer both denied it existed.

one even claimed that the force which kept a motorcyclist on the wall
in the wall of death was the centripetal force.

i lost interest in physics after this.

shouldnt all physics teachers and professors be dragged along to nasa
for compulsory teaching on this subject ?

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  #2  
Old 07-21-2004, 10:27 PM
Donald G. Shead
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Default WHY do some people try and deny the existence of Centrifugal force ?

[Only registered users see links. ] wrote in message news:<[Only registered users see links. ]>. ..

Makes sense to me Sam: Motorcyclists exert - center fleeing -
centrifugal force on the walls of death; which in turn keep them on
the walls with a restraining centripetal force.

They should also learn the difference between concepts, such as weight
and mass; and measures of these concepts.
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  #3  
Old 07-22-2004, 12:04 AM
Steven Gray
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Default WHY do some people try and deny the existence of Centrifugal force ?

[Only registered users see links. ] wrote in news:sphtf05oeh2rsjnfbubvo4qbspgqjoqemu@
4ax.com:


Because as defined by physicists, the centrifugal force is in fact a
fictitious force. Unfortunately, the popular explanations regarding it
generally miss the mark and make for a lot of confusion.


That's wrong, but probably not for the reason you think it is. It's
momentum that keeps the motorcycle against the wall, not the force
exerted by the wall. However, the force exerted by the wall on the
motorcycle is, indeed, a centripetal force, since it's directed toward
the center of the cage.


Why? Whether or not the subject is of interest to you shouldn't depend
on other people's knowledge or lack thereof.

--
Steve Gray
[Only registered users see links. ]
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  #4  
Old 07-22-2004, 10:03 AM
sam1967@hetnet.nl
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Default WHY do some people try and deny the existence of Centrifugal force ?

>
not according to nasa it isnt. it all depends on which reference
frame you choose. the only real forces are the 4 fundamental forces of
nature and all other forces are inertial forces. the centrifugal force
is an inertial force.



not so.

[Only registered users see links. ]

Wind the car up, place it inside the vertical, circular track, and let
go. The car speeds forward, up the track and around. It keeps looping
around the track until the spring is unwound and friction slows it.
Eventually, the car will no longer be able to loop to the top of the
track and around, and gravity will make it fall down.

Why was the car at first, when it went fast, able to loop around the
track, but not later after it had slowed?

Answer: At first, the car's great speed around the circular track
created a lot of centrifugal force. That force pushed it hard against
the track, and the downward force of gravity could not pull it off.
Only after the car had slowed and the centrifugal force became reduced
was gravity able to make it fall.

A general note: Centrifugal force is felt whenever you go quickly
around a curve -- on a merry-go-round, in a car speeding around a
tight curve, or when you swing an object tied to a string in circles
overhead.
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  #5  
Old 07-22-2004, 10:58 AM
Donald G. Shead
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Default WHY do some people try and deny the existence of Centrifugal force ?

[Only registered users see links. ]PAM (Steven Gray) wrote in message news:<Xns952DCC28FBD1sgray2cflrrcom@65.32.1.7>...
Cut<

Except when you know darn well that your teacher is teaching you
wrong:

It's obvious that the motorcyclist is exerting a centrifugal force on
the wall; just as the clothes in a spin dry washer are exerting a
centrifugal force that squeezes the water out of them.
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  #6  
Old 07-22-2004, 03:27 PM
sam1967@hetnet.nl
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Default WHY do some people try and deny the existence of Centrifugal force ?

On 22 Jul 2004 03:58:18 -0700, [Only registered users see links. ] (Donald G. Shead)
wrote:


it was my school physics teacher who first introduced us to circular
motion and we students all argued with him that a centrifugal force
existed in the washing machine and on the wall of death.
he had been taught - badly - that there was no such thing as
centrifugal force and insisted it was centripetal force which kept the
clothes on the drum and the cyclist on the wall.

you could tell he was unhappy about his argument as it clearly made no
sense to him or us.

despite what some people say the education system in the UK (Scotland
especially ) is very outmoded. it is still stuck in a 19th century
model of learning which explains why Scotland has produced no
scientific geniuses for almost 100 years when it used to produce them
by the truck load.

US education seems much more student-centric and more focused on
understanding rather than the dry , pedagogic style common in Scottish
universities.

The NASA article on Centrifugal force is an excellent example of the
US style of teaching compared with the Scottish (University of St
Andrews Maths site being an honorable exception)

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  #7  
Old 07-22-2004, 07:17 PM
Martin Hogbin
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Default WHY do some people try and deny the existence of Centrifugal force ?


<[Only registered users see links. ]> wrote in message news:[Only registered users see links. ]...


That is correct. In a inertial (non-rotating) reference frame there
is no such thing as centrifugal force.

In a rotating reference frame it is necessary to introduce
two new forces if you want to keep the laws of physics
the same as in an inertial frame. The two new forces are
the centrifugal force and the coriolis force.

It is usually better to do physics in an inertial frame
especially when teaching basic physics. In more advanced
physics there are cases where a rotating frame is more
convenient.


The answer depends on which reference frame you use.

Your answer is correct if you use a frame rotating with the car.

Martin Hogbin


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  #8  
Old 07-22-2004, 10:02 PM
Martin Hogbin
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Default WHY do some people try and deny the existence of Centrifugal force ?


<[Only registered users see links. ]> wrote in message news:[Only registered users see links. ]...

You need to fully understand physics in inertial frames
before starting to consider rotating ones.


I doubt it.


Some things, such as large scale meteorology, are better
suited to being explained a rotating frame. Others, such
as the example below are much better considered in an inertial
frame.

A stone is being whirled round on a string. The string is cut
and the stone flies off. Explain what is happening in a reference
frame rotating with the original motion of the stone.

Martin Hogbin


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  #9  
Old 07-23-2004, 05:37 AM
sam1967@hetnet.nl
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Default WHY do some people try and deny the existence of Centrifugal force ?

On Thu, 22 Jul 2004 22:02:53 +0000 (UTC), "Martin Hogbin"
<[Only registered users see links. ]> wrote:

there are two main horizontal forces at work . a centrifugal force
equal to mv^2/ r and a centripetal force provided by the tension in
the string. while the stone is attached to the string the two forces
are in equillibrium. as the velocity of the stone increases the
centrifugal force becomes so great that it passes the tensile breaking
point of the string and the string snaps. ie the Tension in the string
can only go to a maximum level whereas the centrifugal force is
potentially infinite. this is directly analogous to the car going
round a bend and the draughts piece on the turntable.

the stone then flies off in a radial direction.

how is that ?

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  #10  
Old 07-23-2004, 07:21 AM
sam1967@hetnet.nl
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Default WHY do some people try and deny the existence of Centrifugal force ?

On Fri, 23 Jul 2004 06:37:07 +0100, [Only registered users see links. ] wrote:


PS

this answer is for a stone being whirled in a flat horizontal circle.
for a vertical circle the answer is slightly different but the
principle remains the same.

in the horizointal circle if someone cuts the string there is no
longer any Tension in the string to counteract the outward
centre-fleeing (centrifugal) force and the stone flies off in a radial
direction.



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