# Physics - No Such Thing as a 'Pull'? **URL:** \ **Category:** Factual Questions\ **Created:** [August 9, 2010, 1:55am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659 "2010-08-09T01:55:27Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![UncleFred](https://avatars.discourse-cdn.com/v4/letter/u/f0a364/32.png) [@UncleFred](https://boards.straightdope.com/u/UncleFred)\ **Post date:** [August 9, 2010, 1:55am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/1 "2010-08-09T01:55:27Z")
When I was in grade school they brought in a retired scientist each week to deliver lectures, do demonstrations, and otherwise interest us in science. One of the things I still remember was his claim that with regards to forces; there is no such thing as a “pull” and there are only “pushes”. When one student argued that he could “pull” the door of a refrigerator open, the scientist poined out that his hand was really “pushing” on the away side of the handle. All other examples of alleged “pulls” were similarly explained away. Does his statemant hold up? A magnet “attracts” a piece of iron, but I vaguely remember explanations that the field of the magnet is causing perturbations to the far side of the individual magnetic fields of the iron atoms, resulting in a net push. Similarly a gravitational attraction might be explained by some field being lessened (or whatever) on the far side of an item being attracted, also resulting in a net “push”. I apologize for the poor analyses above, and ask; is there such as thing as a ‘pull’ ? ---
**Author:** ![Blut\_Aus\_Nord](https://avatars.discourse-cdn.com/v4/letter/b/9e8a1a/32.png) [@Blut\_Aus\_Nord](https://boards.straightdope.com/u/Blut_Aus_Nord)\ **Post date:** [August 9, 2010, 2:41am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/2 "2010-08-09T02:41:56Z")
Just sounds like semantics to me. Push, pull, whatever. What’s significant is the force being exerted and where that force is coming from. Better though if you wait for someone who knows what they’re talking about. ---
**Author:** ![NinetyWt](https://avatars.discourse-cdn.com/v4/letter/n/cc9497/32.png) [@NinetyWt](https://boards.straightdope.com/u/NinetyWt)\ **Post date:** [August 9, 2010, 2:45am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/3 "2010-08-09T02:45:42Z")
It sounds like he was oversimplifying things. There are such things as tensile forces (as opposed to compressive forces) which pull things apart. Maybe he was trying to say, force is force, no matter which direction it comes from? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [August 9, 2010, 3:14am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/4 "2010-08-09T03:14:00Z")
Technically speaking, at the quantum level there is neither “push” nor “pull”; there is just an exchange of virtual particles that mediate attractive and repulsive forces that results in a change of momentum, although the particles are never in physical contact (and in fact, are distributed as fields). I suppose one could talk about contact forces between “solid” objects as strictly being pushing (repulsive) forces, but by that logic, electric “cling” and magnetic attraction between opposite poles would be pulling forces. In terms of a rigid body (or discrete element of a mechanical continuum) it doesn’t matter whether the force is “pushing” or “pulling”; it acts the same way at the barycenter or boundary condition regardless. Stranger ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [August 9, 2010, 3:46am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/5 "2010-08-09T03:46:31Z")
Fuhgettaboutit. Either you are misremembering, or he was a wacko. If it makes any sense to define a “push” force and connect it to some vernacular meaning of “push”, then there are “pull” forces just as well. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [August 9, 2010, 4:09am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/6 "2010-08-09T04:09:01Z")
Gravity? ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [August 9, 2010, 8:30am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/7 "2010-08-09T08:30:10Z")
Given the engaging curriculum and the nature of the OP, anyone else get the feeling **UncleFred** is a proud graduate of the Midvale School for the Gifted? ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [August 9, 2010, 11:47am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/8 "2010-08-09T11:47:35Z")
I’m guessing he was speaking of contact forces, in which case he’d be “right”. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [August 9, 2010, 1:14pm UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/9 "2010-08-09T13:14:27Z")
So I stick one end of a piece of duct tape onto a smallish object on my desk, and when I \_\_\_\_ on the other end of the duct tape it \_\_\_\_s said object across my desk. Now, I’m pretty sure that \_\_\_\_ wouldn’t be “push,” but if it isn’t “pull,” what is it? ETA: And if \_\_\_\_ is “push,” kindly explain that in English. ---
**Author:** ![Folly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/folly/32/3219_2.png) [@Folly](https://boards.straightdope.com/u/Folly)\ **Post date:** [August 9, 2010, 1:58pm UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/10 "2010-08-09T13:58:22Z")
In Junior High, my Chem teacher was fond of saying, “there’s no sucking in Chemistry!” ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [August 9, 2010, 5:46pm UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/11 "2010-08-09T17:46:52Z")
Speaking as a person who frequently has lectured to students on science…the scientist in the OP sounds like he was either trying to make a deep, philosophical physics point, or just trying to throw the students a humourous curveball. If I pull on a rope, I may be pushing part of the rope along where my hand contacts it - what about the fibers downstream, say a foot away from my hand? I may be pushing upstream, but what’s happening at the other end of the rope? And what pray tell is gravity pushing against - the other side of the molecule? And when I put a steel specimen in a tensile testing rig, what was pushing on what at the fracture point? Something had to be pushing at either side of the crack…but there is nothing. ---
**Author:** ![Rigamarole](https://avatars.discourse-cdn.com/v4/letter/r/77aa72/32.png) [@Rigamarole](https://boards.straightdope.com/u/Rigamarole)\ **Post date:** [August 9, 2010, 6:38pm UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/12 "2010-08-09T18:38:43Z")
> [@Gary\_T](#): > > So I stick one end of a piece of duct tape onto a smallish object on my desk, and when I \_\_\_\_ on the other end of the duct tape it \_\_\_\_s said object across my desk. Now, I’m pretty sure that \_\_\_\_ wouldn’t be “push,” but if it isn’t “pull,” what is it? > > ETA: And if \_\_\_\_ is “push,” kindly explain that in English. The explanation is very simple. You see, _there is no duct tape_. ---
**Author:** ![Folly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/folly/32/3219_2.png) [@Folly](https://boards.straightdope.com/u/Folly)\ **Post date:** [August 9, 2010, 6:50pm UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/13 "2010-08-09T18:50:42Z")
> [@Folly](#): > > In Junior High, my Chem teacher was fond of saying, “there’s no sucking in Chemistry!” Junior High? What the heck was I writing. That was high school of course. ---
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [August 10, 2010, 1:52am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/14 "2010-08-10T01:52:00Z")
and the Civil Engineer will note that you can’t push a rope. ---
**Author:** ![qazwart](https://avatars.discourse-cdn.com/v4/letter/q/5fc32e/32.png) [@qazwart](https://boards.straightdope.com/u/qazwart)\ **Post date:** [August 10, 2010, 2:33am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/15 "2010-08-10T02:33:10Z")
I think many a forces are a “pull” force, like gravity. Gravity doesn’t sneak around in back and push you towards another body. Now, I did have a physics teacher in high school who told me there is no such thing as **centrifugal** force. Centrifugal means the force is pushing the object out from the center. No, if an object is orbiting another object, it’s because **centripetal** forces are pulling the object back into the body it is orbiting. ---
**Author:** ![Rigamarole](https://avatars.discourse-cdn.com/v4/letter/r/77aa72/32.png) [@Rigamarole](https://boards.straightdope.com/u/Rigamarole)\ **Post date:** [August 10, 2010, 2:47am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/16 "2010-08-10T02:47:05Z")
> [@qazwart](#): > > Now, I did have a physics teacher in high school who told me there is no such thing as **centrifugal** force. Centrifugal means the force is pushing the object out from the center. No, if an object is orbiting another object, it’s because **centripetal** forces are pulling the object back into the body it is orbiting. I think the idea behind the “centrifugal force” is, although it’s not a force, it’s the illusion of what you _feel_ when you’re rotating around a center point. Because the force is directed inward but the momentum of your mass wants to keep going straight, the discrepancy gives you a feeling more of being pushed than pulled. ---
**Author:** ![R.P.McMurphy](https://avatars.discourse-cdn.com/v4/letter/r/7993a0/32.png) [@R.P.McMurphy](https://boards.straightdope.com/u/R.P.McMurphy)\ **Post date:** [August 10, 2010, 2:53am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/17 "2010-08-10T02:53:54Z")
I guess it takes us back to the math teacher that said there is no subtraction or division. It is all addition and multiplication although sometimes negative numbers are involved. I guess it makes sense but I never lost any sleep over it. ---
**Author:** ![panamajack](https://avatars.discourse-cdn.com/v4/letter/p/47e85d/32.png) [@panamajack](https://boards.straightdope.com/u/panamajack)\ **Post date:** [August 10, 2010, 3:00am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/18 "2010-08-10T03:00:36Z")
The [last and best word](http://xkcd.com/123/) on centrifugal force as a ‘fictitious force’. ---
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [August 10, 2010, 5:07am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/19 "2010-08-10T05:07:58Z")
> [@qazwart](#): > > Now, I did have a physics teacher in high school who told me there is no such thing as **centrifugal** force. It’s fictitious in the sense that it doesn’t exist if one is (properly) using an inertial (non-rotating) reference frame. Same as the Coriolis force. ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [August 10, 2010, 5:32am UTC](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659/20 "2010-08-10T05:32:56Z")
A lot of people seem to like saying “If you can explain Y by reducing it to X, then there’s no such thing as Y”. That is not necessarily a useful way of putting things, though… [Next page](https://boards.straightdope.com/t/physics-no-such-thing-as-a-pull/549659.md?page=2)