You Have A Helium Balloon In Your Car. What Direction Does It Go When You Accelerate?

If you ’ve ever send helium balloons in your motorcar , perhaps courtesy of a small child who wo n’t allow you store them in the trunk , you may have envision something odd .

When you speed in a elevator car , the seat you are sat in pushes you onward , with the result that you feel like you are being pushed back into it . If you dangle something on the rearview mirror , you will also comment that it will sway backwards as you set out to accelerate .

So what happen to a helium balloon , flying freely inside your vehicle ? Surely it too will be thrown backwards as you speed up in the forwards commission ?

Well , as you may have already intuit , no . That is not the case . As you accelerate forward , the He balloon will be thrown forwards too . It ’s a strange plenty , especially when equate to a balloon occupy with distinctive melody rather than He .

Conversely , when you brake the atomic number 2 balloon will be impel backwards , while an average balloon ( and you ) are propelled in the forward counselling .

So , why is this ? It is because of the density of the gas inside and exterior of the balloon .

Buoyancy is an upward force play in a fluid ( any flowing substance , including air ) exercise on all body within it . The forcefulness comes from the pressure within the fluid being greater the further down the fluid you go . The pressure sensation on the bottom of an object within the fluid is higher than at its top , causing theupwards force .

If the buoyant force of a fluid is greater than the weight of an object placed within it , the physical object will float . Helium , being lighter than the other elements in our atmosphere , rises . It ’s the same when air is heated inside a raging zephyr balloon , make it less dense per intensity inside the balloon than it is outside , induce it to rise .

So , when you accelerate your car forwards , the air within your vehicle slush around backwards , like if you were to speed up a bucket or a jar of water .

This air , ever so slightly promote towards the back of the fomite , creates a floaty force now labor the atomic number 2 balloon towards the front of the vehicle . When you brake , the air moves towards the front of the vehicle , and the buoyancy personnel pushes the balloon backwards , lead in a weird - front core .