# 13-story free-fall G-forces. **URL:** \ **Category:** Factual Questions\ **Created:** [April 22, 2004, 4:22am UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369 "2004-04-22T04:22:59Z")\ **Posts on this page:** 9\ **Page:** 2
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [April 22, 2004, 6:01pm UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369/21 "2004-04-22T18:01:30Z")
Note that the ToT accelerates downwards at a higher rate than gravity: 1.3 g. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 22, 2004, 7:04pm UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369/22 "2004-04-22T19:04:40Z")
A person standing on the surface of the Earth is accelerating upwards at 1 g. A person in free-fall, as on an amusement park ride or in orbit, is not feeling any force, and is therefore not accelerating. Amazingly, the most revolutionary idea in Einstein’s general relativity is the notion that your accelerometer reading really is correct. ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [April 22, 2004, 7:27pm UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369/23 "2004-04-22T19:27:56Z")
> [@Chronos](#): > > A person standing on the surface of the Earth is accelerating upwards at 1 g. A person in free-fall, as on an amusement park ride or in orbit, is not feeling any force, and is therefore not accelerating. Amazingly, the most revolutionary idea in Einstein’s general relativity is the notion that your accelerometer reading really is correct. You didn’t really mean to say a person on the surface is _accelerating_ upwards at 1g, did you? Acceleration is defined as change in velocity wrt time - dv/dt. In the frame of reference of the earth, a person standing on the surface has zero velocity, and therefore by definition has an acceleration of 0 as well. A person in free fall is most definitely accelerating, until he reaches terminal velocity. A person standing on the surface has 2 forces acting on him - gravity pulling him down at mass_1g, ground pushing him up at mass_1g. Net forces are zero, no acceleration. ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [April 22, 2004, 8:08pm UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369/24 "2004-04-22T20:08:20Z")
He _did_ mean to say that. In a relativistic way, if you’re standing on the surface of the Earth, you’re accelerating upwards in curved spacetime. If you’re in free fall, with no external forces, you’re following a straight line and are not accelerating. In this thread, it’s just a question of which semantic standard we want to work with. I tend to think of freefall as zero g. That’s probably because I used to fly small planes, and this is the only sensical way to define acceleration. Straight and level flight is one g. ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [April 22, 2004, 8:44pm UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369/25 "2004-04-22T20:44:54Z")
> [@CurtC](#): > > He _did_ mean to say that. In a relativistic way, if you’re standing on the surface of the Earth, you’re accelerating upwards in curved spacetime. If you’re in free fall, with no external forces, you’re following a straight line and are not accelerating. Ok, but I’m betting the behavior of the Tower of Terror can be explained strictly in the Newtonian regime 😉 ---
**Author:** ![kelly5078](https://avatars.discourse-cdn.com/v4/letter/k/6f9a4e/32.png) [@kelly5078](https://boards.straightdope.com/u/kelly5078)\ **Post date:** [April 22, 2004, 8:49pm UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369/26 "2004-04-22T20:49:48Z")
> [@](#): > > Note that the ToT accelerates downwards at a higher rate than gravity: 1.3 g. How can this be? Does it have an engine? Otherwise, it’s impossible for something to fall with an acceleration greater than that of gravity. ---
**Author:** ![Duderdude2](https://avatars.discourse-cdn.com/v4/letter/d/cdc98d/32.png) [@Duderdude2](https://boards.straightdope.com/u/Duderdude2)\ **Post date:** [April 22, 2004, 8:54pm UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369/27 "2004-04-22T20:54:18Z")
> [@kelly5078](#): > > How can this be? Does it have an engine? Otherwise, it’s impossible for something to fall with an acceleration greater than that of gravity. There are cables attached to both the base and the top of the elevator. This allows it to be pulled in either direction at speeds faster than gravity. ---
**Author:** ![Shade](https://avatars.discourse-cdn.com/v4/letter/s/2bfe46/32.png) [@Shade](https://boards.straightdope.com/u/Shade)\ **Post date:** [April 22, 2004, 10:06pm UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369/28 "2004-04-22T22:06:08Z")
> [@Dag Otto](#): > > No, you would feel zero G. The platform is moving at a constant velocity of 10 m/s. You are moving at a constant velocity of 10 m/s. The ball is moving at a constant velocity of 10 m/s. Nothing is being accelerated. :smack: :smack: :smack: I meant 10m/s/s. I SWEAR that’s what I wrote. Obviously your speed is irrelevent as I didn’t give a reference point. Sorry, I only confused the issue there. ---
**Author:** ![Tabby\_Cat](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Tabby\_Cat](https://boards.straightdope.com/u/Tabby_Cat)\ **Post date:** [April 22, 2004, 10:32pm UTC](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369/29 "2004-04-22T22:32:01Z")
> [@CurtC](#): > > In this thread, it’s just a question of which semantic standard we want to work with. I tend to think of freefall as zero g. That’s probably because I used to fly small planes, and this is the only sensical way to define acceleration. Straight and level flight is one g. Now that I think about it, zero g makes perfect sense in describing such a situation. If it didn’t, then there would be no meaning to 2g, or 5g, or whatever else g, since on Earth the default would be 1g. Therefore, it cannot be a question of sementics, as the measurement term “g” would lose significance for most people if there were any other meaning. To provide an example of why defining “g” as simply the acceleration due to gravity is meaningless in this situation, imagine a lift decending at 9.8m/s^2 with a person inside, and the same setup in space, but not accelerating. The theory of relativity states that the person in both situations will not be able to tell the difference in the 2 situations. Therefore, if “g” is to have any meaning in the above situation, it must be that of the “force experienced by a person on Earth due to gravity”, and not simply the physics constant “g”. [Previous page](https://boards.straightdope.com/t/13-story-free-fall-g-forces/241369.md?page=1)