Money Under Bottle Trick | Inertia Science Experiment
This is an activity that uses friction and inertia in unexpected ways. But, you might make some quick cash.
Money Under Bottle Trick: A Lesson in Inertia and Friction
This is an activity that uses friction and inertia in unexpected ways. (Added bonus: You might make some quick cash!)
The setup of this money under bottle trick looks an awful lot like a one-container version of the famous “tablecloth trick.” You might be able to present it that way, too. Of course, it’s important that you leave out that fact that it’s basically just the opposite of that well-known “yank the cloth out from under the table setting” stunt. Borrow some paper currency from a friend, grab an empty soda bottle, find an open table and get ready to learn about physics in this friction and inertia experiment. The game is afoot!
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- Paper currency
- Empty, longneck soda bottle
- Smooth table top
- Adult supervision
Smooth the currency onto a clean, flat surface. Place the bottle open end down on top of the money in about the center off the bill. Steady the bottle carefully.
Tell your friend you’ll add the same amount of money after the currency is pulled out from under the bottle if (1) the bottle isn’t touched and (2) the bottle doesn’t fall over.
Watch the efforts fail… watch them fail a lot! Just don’t laugh.
Offer to try it, too, but if you actually do it, you get to keep the money.
Start to carefully roll up the currency from one end and roll towards the bottle.
When the rolled up bill gets to the mouth of the bottle, continue rolling but be careful to slowly nudge the bottle towards the far edge of the currency. Gently push the bottle in tiny increments as you roll up the bill.
Be patient and you’ll pocket the winnings!
How Does It Work
Inertia comes from Newton’s first law of motion, which states that an object in motion (or at rest) tends to stay in motion (or at rest) unless a force acts on it to change its speed, to stop it, to change its direction or to get it moving. Think of ball rolling down a hill — the first law of motion in Newton’s mathematical equation demonstrates that the ball is likely to continue to roll, unless you stop that ball, pick it up and give it a kick in the opposite direction. In this friction and inertia experiment, this particular balanced bottle wants to stay in the position it is in; you, on the other hand, want to get that cash.
In other activities (like our famous Tablecloth Trick), you’ve seen how sudden, quick motions have been used to overcome inertia successfully. In this particular inertia experiment, however, the safe removal of that money isn’t achieved through those sudden, quick motions. On the contrary, this money under bottle trick demonstrates just the opposite: just like Aesop’s fable with the tortoise and the hare, slow and steady wins the race. When you attempt to remove the dollar bill by pulling it out, you apply an outside force that causes the bottle to topple every time. Game over.
This is a case where “friction” takes center stage; you have to be ready to work around it. There is some serious friction between the bill and the bottle — as well as the bill and the tabletop. There is so much friction, in fact, that the bill pulls the empty bottle with it every time. To reduce the impact of friction, you have to roll the currency right up to the edge of the bottle opening and then nudge and coax the bottle to slide, little by little, as you roll. It’s a slow-moving process that doesn’t give enough force to tip the bottle.
There are some really amazing inertia experiments (like Newton’s Beads, Inertia Ring and our famous Tablecloth Trick) and physics experiments to be explored here on our website. At Steve Spangler Science, we have super cool hands-on experiments for kids that demonstrate these complex scientific principles in a way they understand. We add that Steve Spangler Science WOW factor to each and every inertia experiment, including our money under bottle trick. Don’t miss other science fair project ideas and at-home experiments. Whether you’re looking for fun after-school activities or demonstrations and experiments that will get ooohs and ahhhs from your class, we have a ton of ideas to browse!
Take It Further
Of course, the assumption is that you’ll be using older bills that may be a bit crumpled and dirty. Both of those factors will increase friction. Although old, crumpled bills ideally demonstrate friction, it’s also important to practice with those crisp, hot-off-the-press bills — just to make sure you know what to expect with one. In either case, rolling the bill is a sure winner!