# Haunted Pickup? **URL:** \ **Category:** General Discussion\ **Tags:** sierra1500, gmc\ **Created:** [February 23, 2019, 11:32pm UTC](https://community.cartalk.com/t/haunted-pickup/135259 "2019-02-23T23:32:12Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Sarrah\_Camp](https://avatars.discourse-cdn.com/v4/letter/s/ea5d25/32.png) [@Sarrah\_Camp](https://community.cartalk.com/u/Sarrah_Camp)\ **Post date:** [February 23, 2019, 11:32pm UTC](https://community.cartalk.com/t/haunted-pickup/135259/1 "2019-02-23T23:32:12Z")
Hi there! I’m a bartender posting on behalf of my regular, Steve. Steve had a GMC Sierra pick up. When he placed a helium balloon in the passanger seat, the balloon leaned forward when accelerating, backwards when breaking. That’s backwards, what’s up with that? Steve said he would turn the air off completely and the windows rolled up. Can anyone explain these backwards physics? ---
**Author:** ![shanonia](https://avatars.discourse-cdn.com/v4/letter/s/9de053/32.png) [@shanonia](https://community.cartalk.com/u/shanonia)\ **Post date:** [February 23, 2019, 11:36pm UTC](https://community.cartalk.com/t/haunted-pickup/135259/2 "2019-02-23T23:36:40Z")
Newton and Einstein have weekends off, but you might get some interesting ideas in the mean time. ---
**Author:** ![Sarrah\_Camp](https://avatars.discourse-cdn.com/v4/letter/s/ea5d25/32.png) [@Sarrah\_Camp](https://community.cartalk.com/u/Sarrah_Camp)\ **Post date:** [February 23, 2019, 11:37pm UTC](https://community.cartalk.com/t/haunted-pickup/135259/3 "2019-02-23T23:37:48Z")
We’re definitely interested in what everyone has to say! Thank you for letting us know they have weekends off. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [February 23, 2019, 11:54pm UTC](https://community.cartalk.com/t/haunted-pickup/135259/4 "2019-02-23T23:54:41Z")
It’s the same reason a helium balloon goes up when you release it, rather than like most stuff, which goes down. It’s lighter than air, so like anything lighter than something else, it moves toward the top; i.e. upward. A helium balloon moves backward – counterintuitively – when stopping b/c when braking the air mass inside the passenger compartment gets thrown & squished toward the front of the car, making the air near the front of the car more dense, which forces the balloon (being less dense) to the rear. The helium balloon always moves away from areas of more dense air. This is an experiment which is hard to do, but if you could measure the upward force on the same balloon, it would be more at sea level than in Denver, b/c the air is more dense at sea level. I’m thinking this is something a person could make a little extra cash on in a bar bet … hmmm … 😉 ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [February 24, 2019, 12:24am UTC](https://community.cartalk.com/t/haunted-pickup/135259/5 "2019-02-24T00:24:51Z")
And when you accelerate the balloon goes forward, and when you stop it goes backwards. I am not sure but always figured it was air acting like water. You accelerate the air moves to the back creating higher pressure so the balon moves to the front. Ready for more theories. ---
**Author:** ![tcmichnorth](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tcmichnorth/32/25126_2.png) [@tcmichnorth](https://community.cartalk.com/u/tcmichnorth)\ **Post date:** [February 24, 2019, 2:00am UTC](https://community.cartalk.com/t/haunted-pickup/135259/6 "2019-02-24T02:00:29Z")
I think we found our Einstein wasn’t out for the weekend after all, he just changed his name to @George_San_Jose1 ---
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [February 24, 2019, 8:46pm UTC](https://community.cartalk.com/t/haunted-pickup/135259/7 "2019-02-24T20:46:51Z")
This was a question in my freshman physics exercise book. @George_San_Jose1 has it right. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [February 24, 2019, 10:49pm UTC](https://community.cartalk.com/t/haunted-pickup/135259/8 "2019-02-24T22:49:15Z")
> [@Sarrah\_Camp](#): > > the balloon leaned forward when accelerating, backwards when **breaking**. If you can be more specific regarding exactly what **broke** , we might be able to provide a good response. Was he in the act of braking when something was broken? 🤔 ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [February 25, 2019, 12:55am UTC](https://community.cartalk.com/t/haunted-pickup/135259/9 "2019-02-25T00:55:11Z")
> [@RandomTroll](#): > > This was a question in my freshman physics exercise book It’s a common question when interviewing potential new hires for silicon valley high tech engineering jobs. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [February 25, 2019, 1:19am UTC](https://community.cartalk.com/t/haunted-pickup/135259/10 "2019-02-25T01:19:01Z")
Then you can answer why are manhole covers round instead of square! ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [February 25, 2019, 1:24am UTC](https://community.cartalk.com/t/haunted-pickup/135259/11 "2019-02-25T01:24:34Z")
That used to be a common interview question too. But it isn’t used so much anymore for some reason. One question that’s still used I think is : say you woke up one day and found you were the size of an ant. everything, all body parts, in proportion otherwise. other than being smaller, would you notice anything else unusual? ---
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [February 25, 2019, 5:59pm UTC](https://community.cartalk.com/t/haunted-pickup/135259/12 "2019-02-25T17:59:01Z")
Think about what would happen if the balloon were outside the car.