let's use Newton's third law to make a foam ball cannon in order to make a cannon that shoots 6-inch foam balls this is what dr. Smith is using a five foot long and four inch inner diameter PVC pipe and you can use either an end cap or an adapter with a screw cap dr. Smith prefers the screw cap because it allows access to inside the cannon for cleaning and drying purposes it also lets you rapidly air out the cannon between firings dr. Smith is working in a well-ventilated area because the fumes from the PVC primer and cement are quite strong dr. Smith is being sure to follow the instructions closely on applying the primer and cement to the pipe and adapter he is now going to drill a hole roughly 12 inches from the adapter the size of the hole matches the size of the barbecue lighter that he is going to use to ignite the vapors in the cannon when complete he's going to let the cannon set and ventilate overnight as a precaution now it's time to fire the cannon dr. Smith is putting a pipette full of denatured ethanol in the mouth of the cannon and quickly inserting the foam ball to trap the explosive vapors you can also try using isopropanol he is now adding the same amount of fuel through the ignition hole of the cannon he is spinning the cannon around that helps spread the fuel around and give it all vaporized inside the cannon it is best to wait a couple minutes to ensure all the fuel is vaporized if you use isopropanol or a rubbing alcohol you may want to wait a little bit longer dr. Smith is making sure the cannon is well secured and not going to hit anyone when you pull the trigger on the barbecue lighter the volatile fumes inside the cannon will ignite and greatly expand blowing out the foam ball from the cannon