Balloon in a car...

[w=f[z]]

Here is a little question;

Let's say you are driving along in your car on a cold-autumn day. You have a passenger in the center of the back seat that is holding a helium-filled balloon in front of them by the string. You make a sharp left turn around a bend in the road.

 

Which way does the balloon move relative to the car?

(Justify your answer.)

 

Cheers,

w=f[z]

 

 

 

P.S. I'm still really new here, so my apologies if this has already been discussed.

[YT2095]

it`ll move to the right the same as you do.

 

Justification: preservation of Inertial forces.

[insane_alien]

it'll move to the left.

 

justification, buoyancy. the air is heavier than the balloon.

 

if it was a air filled balloon i would agree with YT

[w=f[z]]

it`ll move to the right the same as you do.

 

Justification: preservation of Inertial forces.

 

Hi YT,

This problem has been known to confuse physicists a time or two.

 

You might want to reconsider....

 

Cheers

[YT2095]

IA, it makes no difference what the balloon is filled with as long it has MASS, it`s subject to the same force

[w=f[z]]

it'll move to the right.

 

justification, buoyancy. the air is heavier than the balloon.

 

if it was a air filled balloon i would agree with YT

 

Did you mean left IA?

[YT2095]

he meant Left so did I

 

damn our rotten mistyping keyboards!

[w=f[z]]

Just so we're all clear on this...

If we turn left (as in the problem), and say we have a ball resting on the dashboard, the ball will move right relative to the car. Yes?

 

Cheers

[YT2095]

naah it`ll go left also, sure it will, it`s got He gas in it

 

although I`ve no idea HOW you`ll make it "Rest" on the dashboard????

[timo]

A helium-filled balloon resting on the dashboard? It won't move relative to the car at all since it's squeezed too tightly between the dashboard and the windshield .

[w=f[z]]

;344715']Just so we're all clear on this...

If we turn left (as in the problem)' date=' and say we have a ball resting on the dashboard, the ball will move right relative to the car. Yes?

 

Cheers[/quote']

 

Note here I mean ball - not balloon. Perhaps I should have said coin or something else of that nature. D'oh!

[insane_alien]

;344712']Did you mean left[/i'] IA?

 

i said left.

 

/me shiftily draws attention away from the editted notification.

 

A, it makes no difference what the balloon is filled with as long it has MASS, it`s subject to the same force

 

yeah but if it is less dense than aire then it'll move left, if it is more dense then it will move right

[YT2095]

ok, NOW I`m officially confused

[insane_alien]

okay, take it to the extreme situation.

 

you have a tank half filled with water(half empty if you're one of those people) with a little boat floating on it. it just so happens this tank is on the end of a centrifuge. whe you start of the water will be level and the boat is on top. as it spins faster and faster, the water will rotate so he surface is nearly perpendicular to the ground. the boat will still be floating on he surface as if nothing has happened.

[richard]

Right, inertia.

[D H]

IA is right, it moves to the left.

 

This left/right business is making it apparent that SFN members may have some dyslexic tendencies. To avoid confusion, why don't ya'll talk about what happens to a helium-filled balloon in a moving car that suddenly comes to a stop?

[insane_alien]

tried it, it goes left.

 

yes i specifically went out and bought a helium balloon to check my hypothesis.

[Klaynos]

What if it's a convertible with the roof down?

[D H]

I noticed this effect when one of my kids was holding a balloon in the car. The balloon went forward when I accelerated and backward when I applied the brakes.

[w=f[z]]

What if it's a convertible with the roof down?

 

Bingo!

 

Read the original post carefully and see if you spot my subtle hint....

 

Cheers

[Klaynos]

;344789']Bingo!

 

Read the original post carefully and see if you spot my subtle hint....

 

Cheers

 

Cold autumn day so you'd have the car nicely sealed up

[swansont]

i_a is right, and D H's point is well-taken. 1-D is better than 2-D.

 

Newton's first law: an object that's in motion remains in motion, and all that.

 

Driver hits the brakes, and everthing has the tendency to continue to move forward. "Everything" includes the air in the car. Since that is more dense than the He-balloon, the balloon will actually move backward, i.e. in the direction of the acceleration, because it is displaced by the air.

 

Do it in a vacuum, and it will behave as you would expect for a generic mass. (But do it with a remote-controlled car)

[Rasori]

I think you'd be hard-pressed to have a helium-filled balloon in a vacuum.

[J.C.MacSwell]

I think you'd be hard-pressed to have a helium-filled balloon in a vacuum.

 

It would of course roll around on the floor.

[Rasori]

It would of course roll around on the floor.

 

The matter is the balloon: the pressure difference between the vacuum and the inside of the balloon would not last. The pressures would attempt to equalize, eventually ending in the popping of the balloon.