# Floating magnets and gravity **URL:** \ **Category:** Factual Questions\ **Created:** [June 3, 2001, 5:03am UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399 "2001-06-03T05:03:06Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Homer](https://avatars.discourse-cdn.com/v4/letter/h/df788c/32.png) [@Homer](https://boards.straightdope.com/u/Homer)\ **Post date:** [June 3, 2001, 5:03am UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/1 "2001-06-03T05:03:06Z")
If a magnet is using it’s opposing force to hold another magnet in the air, what happens to the weight? Is the ‘supporting’ magnet receiving pressure equal to the weight of the ‘floating’ magnet? –Tim ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [June 3, 2001, 5:31am UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/2 "2001-06-03T05:31:58Z")
Sure it is. Peace, mangeorge ---
**Author:** ![BigGiantHead](https://avatars.discourse-cdn.com/v4/letter/b/b4bc9f/32.png) [@BigGiantHead](https://boards.straightdope.com/u/BigGiantHead)\ **Post date:** [June 3, 2001, 5:49am UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/3 "2001-06-03T05:49:32Z")
Nothing “happens to the weight,” in any meaningful sense. Weight is merely the downward force on an object due to the acceleration of gravity, _f=m•a_. ‘F’ here is the weight, ‘a’ the gravity (9 m/sec[sup]2[/sup], or 32 ft/sec[sup]2[/sup] if you like). The two magnets act on each other just like two identical non-magnetic bricks would - except with an air space between. The lower one provides enough upward force to the upper one to arrest its further downward motion; the upper pushes down on the lower. Because of this, the lower one is pressed into the tabletop (or whatever), with the weight of two magnets/bricks: its own and the upper one’s. Which is a periphrastic way of saying ‘Yes.’ 😉 - Dave ---
**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:** [June 3, 2001, 6:39am UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/4 "2001-06-03T06:39:23Z")
Yes Tim, the lower one bears the weight of the upper one. ---
**Author:** ![Fern\_Forest](https://avatars.discourse-cdn.com/v4/letter/f/71c47a/32.png) [@Fern\_Forest](https://boards.straightdope.com/u/Fern_Forest)\ **Post date:** [June 3, 2001, 7:04am UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/5 "2001-06-03T07:04:41Z")
yeah, gravity is really really really really weak compared to the other forces ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [June 3, 2001, 12:43pm UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/6 "2001-06-03T12:43:38Z")
Yes, by Newton’s 3rd Law: “For every action there is an equal and opposite reaction,” a statement known by all but misunderstood by most. Longer but more understandable version: “If 2 bodies interact (via gravity, electromagnetism, contact, etc.), the force exerted by body 1 on body 2 is equal in magnitude and opposite in direction to the force exerted by body 2 on body 1.” So if magnet 1 is exerting a repulsive upward force on magnet 2 equal to magnet 2’s weight, magnet 2 must be exerting a repulsive downward **force** (not pressure) on magnet 1 that is also equal in magnitude to magnet 2’s weight. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [June 3, 2001, 12:46pm UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/7 "2001-06-03T12:46:23Z")
> [@](#): > > \*Originally posted by brother rat \* > \*\*yeah, gravity is really really really really weak compared to the other forces \*\* True, but how is this relevant here? ---
**Author:** ![Fern\_Forest](https://avatars.discourse-cdn.com/v4/letter/f/71c47a/32.png) [@Fern\_Forest](https://boards.straightdope.com/u/Fern_Forest)\ **Post date:** [June 3, 2001, 1:13pm UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/8 "2001-06-03T13:13:09Z")
> [@](#): > > \*Originally posted by robby \* > \*\* > > > [@](#): > > > > \*Originally posted by brother rat \* > > \*\*yeah, gravity is really really really really weak compared to the other forces \*\* > > True, but how is this relevant here? \*\* um, just saying that the magnet will have pretty much no problem overcoming almost anything that gravity can throw at it. it was basically my way of saying me too, maybe expand a little on the theme. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [June 3, 2001, 3:18pm UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/9 "2001-06-03T15:18:25Z")
> [@](#): > > \*Originally posted by brother rat \* > \*\*yeah, gravity is really really really really weak compared to the other forces \*\* But the gravitational force on the magnet is equal to the magnetic force on it. The downward pull of gravity is exactly counteracted by the magnetic force pushing it up. Otherwise it’d fly up or fall down. (Or to be exact, it would move up or down to a position where they are equal.) ---
**Author:** ![Dr.Lao](https://avatars.discourse-cdn.com/v4/letter/d/2bfe46/32.png) [@Dr.Lao](https://boards.straightdope.com/u/Dr.Lao)\ **Post date:** [June 3, 2001, 6:06pm UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/10 "2001-06-03T18:06:51Z")
> [@](#): > > \*Originally posted by robby \* > \*\* > > > [@](#): > > > > \*Originally posted by brother rat \* > > \*\*yeah, gravity is really really really really weak compared to the other forces \*\* > > True, but how is this relevant here? \*\* The entire Earth (5.98 x 10[sup]24[/sup] kg) is pulling down on the floating magnet, but that is overcome by a 5 g magnet pushing up. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [June 3, 2001, 8:52pm UTC](https://boards.straightdope.com/t/floating-magnets-and-gravity/67399/11 "2001-06-03T20:52:25Z")
> [@](#): > > \*Originally posted by Dr. Lao \* > \*\* > > > [@](#): > > > > \*Originally posted by robby \* > > \*\* > > > > > [@](#): > > > > > > \*Originally posted by brother rat \* > > > \*\*yeah, gravity is really really really really weak compared to the other forces \*\* > > > > True, but how is this relevant here? \*\* > > The entire Earth (5.98 x 10[sup]24[/sup] kg) is pulling down on the floating magnet, but that is overcome by a 5 g magnet pushing up. \*\* Indeed–I have used that very example in class. I didn’t see what that had to do with the OP, though. This whole discussion could have taken place with a normal force replacing the magnetic force. In any case, I made that comment well before my coffee this morning. 🙂