If you have a middle school kid you know about bottle flipping. You are fed up with bottle flipping. You will lose your flipping mind if you hear another bottle flip.

Since your kids are flipping out already, why not turn it into a science experiment?

For those not familiar with this flipping fad, here’s what it’s all about. Kids spend hours (not exaggerating here) trying to toss a mostly empty plastic water bottle so it lands exactly upright. On its bottom is good, on its top is instant flipping fame.

Yep, that’s it. Flipping a bottle.

Doesn’t take much to amuse kids these days.

So what’s the science?

The basic technique is to fill the bottle only about 1/3 of the way full. Grab the bottle by the top and start it spinning as you toss it onto a nearby table.

The keys are in the center of gravity and angular momentum

Center of gravity is where the mass of an object is centered and more importantly the point around which the object spins.

Angular momentum is the tendency of an object to continue spinning. It depends on the mass, size of the object and how fast it is spinning.

When you first grab the bottle it is upright so the water (and almost all the mass) is in the bottom of the bottle.

When you toss the bottle it starts spinning around the lid, where you were holding the bottle. The water sloshes around as the bottle starts to spin.

Gradually the angular momentum or spinning motion is transferred to the more massive water so the spinning motion of the bottle slows down to almost nothing. At this point the bottle simply falls straight down due to gravity landing upward.

The key to landing upright is to put just the right amount of spin on the bottle and to have just the right amount of water to slow down that spinning as it lands.

Try this

  • Experiment with different amounts of water. Start with the bottle 1/3 full, then pour out a little at a time or add small amounts.
  • Does it matter what kind of water bottle you use? Try different shapes and sizes. Can you flip a 2-liter soda bottle?
  • What if the liquid flows slower than water? Add cornstarch to the water to thicken and slow the flow of the liquid.
  • How do you get a bottle to land on its lid? Try starting the flip by holding the top of the bottle, throwing the bottle higher in the air or using a faster flip.

You can find more bottle flipping science here and the original video that started this flipping fad below.

Bottle Flipping Science
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