Let’s take a good look at Newton’s Laws in motion while making something that flies off in both directions. This experiment will pop a cork out of a bottle and make the cork fly go 20 to 30 feet, while the vehicle moves in the other direction!

This is an outdoor experiment. Be careful with this, as the cork comes out with a good amount of force. (Don’t point it at anyone or anything, even yourself!)

Here’s what you need to find:

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• toy car
• baking soda and vinegar (OR alka-seltzer and water)
• tape
• container with a tight-fitting lid (I don’t recommend glass containers… see if you can find a plastic one like a film canister or a mini-M&M container.)

There are two ways to do this experiment. You can either strap the bottle to the top of a toy car and use baking soda and vinegar, OR use effervescent tablets (like generic brands of alka seltzer) with this modified pop rocket (which you can strap to a toy car, or add wheels to the film canister itself by poking wooden skewers through milk jug lids for wheels and sliding the skewer through a straw to make the axle). Both work great, and you can even do both! This is an excellent demonstration in Newton’s Third Law, inertia, and how stuff works differently here than in outer space. Here’s what you do:

1. Strap the bottle to the top of the toy car or bus with the duct tape. You want the opening of the bottle to be at the back of the vehicle.

2. Put about one inch of vinegar into the bottle.

3. Shove a wad of paper towel as far into the neck of the bottle as you can. Make sure the wad is not too tight. It needs to stick into the neck of the bottle but not too tightly.

4. Pour baking soda into the neck of the bottle. Fill the bottle from the wad of paper all the way to the top of the bottle.

5. Now put the cork into the bottle fairly tightly. (Make sure the corkscrew didn’t go all the way through the cork, or you’ll have leakage issues.)

6. Now tap the whole contraption hard on the ground outside to force the wad of paper and the baking soda into the bottle.

7. Give the bottle a bit of a shake.

8. Set it down and watch. Do not stand behind the bus where the cork will shoot.

9. In 20 seconds or less, the cork should come popping off of the bottle.

What you should see is the cork firing off the bottle and going some 10 or 20 feet. The vehicle should also move forward a foot or two. This is Newton’s Third law in action. One force fired the cork in one direction. Another force, equal and opposite, moved the car in the other direction. Why did the car not go as far as the cork? The main reason is the car is far heavier then the cork. F=ma. The same force could accelerate the light cork a lot more than the heavier car.

Click here to go to next lesson on Inertia and the Second and Third Law.

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