Editing 123: Centrifugal Force

[[Black Hat]] has strapped {{w|James Bond}} to a centrifuge and claims the {{w|Centrifugal force|centrifugal}} force will be lethal. Bond objects that there is no such thing, but just {{w|Centripetal force|centripetal}} force. The notion of centrifugal force is a common one, as we experience it whenever we turn. Teachers will initially teach Newtonian mechanics in an inertial frame, and in inertial frames, the centrifugal force is zero. Instead, a body that moves in a circle does so because of a centripetal force (acting towards the centre of the rotation). This is a reasonable, and correct view, but is a subtle point that many students find hard to grasp, as it seems to contradict their personal experience of centrifugal forces. For the sake of exposition, teachers may claim that "There is no such thing as centrifugal force." This however is also a misconception, which is addressed in the explanation below:

Teachers of mechanics are well aware of this; however, in introductory expositions, these ideas are often not taught. In theoretical mechanics, one describes the positions and velocities of the particles in a model relative to a frame of reference. This means that a time is chosen to be time 0, and positions are chosen to be (0,0,0), (1,0,0), (0,1,0) and (0,0,1). With these chosen, the position and time of any particle in the system can be described. It is an axiom of Newtonian Mechanics that there exist "Inertial Frames." In an inertial frame, a particle will remain at rest or at a constant speed unless acted on by an external force, and Newton's second law takes a simple form: F = ma. The surface of the Earth approximates an inertial frame. In a non-inertial frame, such as one rotating with a giant centrifuge, or moving with an accelerating vehicle, a particle will accelerate, relative to the frame. Newton's second law, when formed in such a frame, is much more complicated, as it has terms for the linear acceleration of the frame, the angular acceleration of the frame, the centrifugal force, and the {{w|Coriolis force}}. These extra terms are sometimes called "fictitious forces," as they result from the choice of the frame of reference. The mathematics required to describe problems in a non-inertial frame is more sophisticated, and all problems may be solved using an inertial frame. Thus is reasonable that teachers at school level "{{w|lie to children}}" and teach the mechanics in inertial frames.

The final statement by Black Hat is that said by {{w|Auric Goldfinger}} in {{w|Goldfinger (film)|Goldfinger}} in response to James Bond's question "Do you expect me to talk?"

The title text is inspired by {{w|Dead or Alive (band)|Dead or Alive's}} famous song from 1985, "{{w|You Spin Me Round (Like a Record)|You Spin Me Round}}".

Randall feels very strongly that the centrifugal force is a real thing. He links to this comic in the first footnote of his [[what if?|What if?]] article [https://what-if.xkcd.com/92/ One-Second Day] and the 6th footnote of [https://what-if.xkcd.com/157/ Earth-Moon Fire Pole], stating that it is a real thing, and that he will go so far as to strap arguers to a centrifuge that he or someone he knows apparently owns.

As can also be seen in the [https://twitter.com/bohacekp/status/531500491180875776/photo/1 footnote on page 132] in his [[what if?#The book|What if? book]], he will even fight you about it. From the book:<br>  

:[James Bond is strapped to a giant wheel suspended from the ceiling. Black Hat is standing next to two levers.]

:Black hat: How do you like my centrifuge, mister Bond? When I throw this lever, you will feel centrifugal force crush every bone in your body.

:Black hat: A laughable claim, mister Bond, perpetuated by overzealous teachers of science. Simply construct Newton's laws in a rotating system and you will see a centrifugal force term appear as plain as day.