Hovercraft transport people and their stuff across ice, grass, swamp, water, and land. Also known as the Air Cushioned Vehicle (ACV), these machines use air to greatly reduce the sliding friction between the bottom of the vehicle (the skirt) and the ground. This is a great example of how lubrication works – most people think of oil as the only way to reduce sliding friction, but gases work well if done right.
In this case, the readily-available air is shoved downward by the pressure inside of balloon. This air flows down through the nozzle and out the bottom, under the CD, lifting it slightly as it goes and creating a thin layer for the CD to float on.
Although this particular hovercraft only has a 'hovering' option, I'm sure you can quickly figure out how to add a 'thruster' to make it zoom down the table! (Hint - you will need to add a second balloon!)
Here's what you need:
[am4show have='p8;p9;p10;p37;p151;p92;' guest_error='Guest error message' user_error='User error message' ]
Download Student Worksheet here.
There's air surrounding us everywhere, all at the same pressure of 14.7 pounds per square inch (psi). You feel the same force on your skin whether you're on the ceiling or the floor, under the bed or in the shower. An interesting thing happens when you change a pocket of air pressure - things start to move.
This difference in pressure causes movement that creates winds, tornadoes, airplanes to fly, and the air to rush out of a full balloon. An important thing to remember is that higher pressure always pushes stuff around. While lower pressure does not "pull," we think of higher pressure as a "push".
The stretchy balloon has a higher pressure inside than the surrounding air, and the air is allowed to escape out the nozzle which is attached to the water bottle cap through tiny holes (so the whole balloon doesn't empty out all at once and flip over your hovercraft!) The steady stream of air flows under the CD and creates a cushion of air, raising the whole hovercraft up slightly... which makes the hovercraft easy to slide across a flat table.
Want to make an advanced model Hovercraft using wires, motors, and leftovers from lunch? Then click here.
[/am4show] [am4show have='p9;p39;' guest_error='Guest error message' user_error='User error message' ] Advanced students: Download your Hovercraft Lab here. [/am4show]
In this case, the readily-available air is shoved downward by the pressure inside of balloon. This air flows down through the nozzle and out the bottom, under the CD, lifting it slightly as it goes and creating a thin layer for the CD to float on.
Although this particular hovercraft only has a 'hovering' option, I'm sure you can quickly figure out how to add a 'thruster' to make it zoom down the table! (Hint - you will need to add a second balloon!)
Here's what you need:
[am4show have='p8;p9;p10;p37;p151;p92;' guest_error='Guest error message' user_error='User error message' ]
- 7-9" balloon
- water bottle with a sport-top (see video for a visual - you can also use the top from liquid dish soap)
- old CD
- paper cup (or index card)
- thumbtack
- hot glue gun
- razor with adult help
Download Student Worksheet here.
There's air surrounding us everywhere, all at the same pressure of 14.7 pounds per square inch (psi). You feel the same force on your skin whether you're on the ceiling or the floor, under the bed or in the shower. An interesting thing happens when you change a pocket of air pressure - things start to move.
This difference in pressure causes movement that creates winds, tornadoes, airplanes to fly, and the air to rush out of a full balloon. An important thing to remember is that higher pressure always pushes stuff around. While lower pressure does not "pull," we think of higher pressure as a "push".
The stretchy balloon has a higher pressure inside than the surrounding air, and the air is allowed to escape out the nozzle which is attached to the water bottle cap through tiny holes (so the whole balloon doesn't empty out all at once and flip over your hovercraft!) The steady stream of air flows under the CD and creates a cushion of air, raising the whole hovercraft up slightly... which makes the hovercraft easy to slide across a flat table.
Want to make an advanced model Hovercraft using wires, motors, and leftovers from lunch? Then click here.
[/am4show] [am4show have='p9;p39;' guest_error='Guest error message' user_error='User error message' ] Advanced students: Download your Hovercraft Lab here. [/am4show]
You’re right! There is no propeller with the simple hovercraft. The air movement comes from the deflating balloon.
How and where do I attach the hovercraft propellers? I am thinking maybe along the bottom or sides of the CD. Or are they needed for the advanced hovercraft?
Really fun and easy to make!!!!!!!
my dog loves this experiment he chases it around the floor he’s already popped a balloon he also guards it when its done zooming around the floor he sits by it until i fill the balloon up again!!!!!!!!!!!!!!!!!!!!!!
Feel free to try a foam cup.
would a foam cup work???
Sorry for the confusion with the links! The second thruster is when you add another balloon, and somehow make it so that the end of the balloon is horizontal (you can use a straw taped to the open end to help you with this – I used a clothespin to keep the air from coming out while I was putting it together). You need some kind of *push” in the horizontal direction to make the hovercraft move forward. I’ve found that a smaller balloon works well for the thruster, because anything larger made mine go off balance. Give it a try!
Hi, sorry if I sent this twice. I posted it and it did not show up. I was trying to make the thruster with another balloon for the hover craft, but I was Unsuccessful. At first I taped a balloon to the back of the balloon on the hover craft, blew it up, and let the air out so it made the whole thing topple over. Then I added a cap to the new balloon to regulate it’s power, but that didn’t seem to do anything. So I looked through the comments and saw that you had posted a link on how to do that. But it brought me to a page where it showed the different grade levels with pictures above them. I was wondering if you could send another link or if you could just teach me how to do it. Have a nice day!!!!
Hey Aurora, I looked through the comments and saw that you posted a link for how to make a thruster using a balloon in order to make it zoom across the table, but when I click the link it just brings me to a page that shows all the grade levels in a list and then next to that it shows the grade levels with pictures above them. I was wondering if you could resend the link, or maybe if you could teach me how to do it. I tried taping another balloon behind the first one controlling the air with another cap, but it didn’t seem to do anything. When I did it without the cap, it made the hole thing fall over. Can you please help me? Have a nice day!
I’ll have Tonya connect with you – your account may not be set up right if you’re able to leave comments but not see the videos.
The videos are not working?
You said in the little intro above the video that you can make it zoom across the table and you gave us a hint, add another balloon. can you tell me where to put it or how to do it?
Yes that’s right! Really any balloon will work. You just want one large enough so that it will hold enough air for the experiment.
Wait is a “7-9” balloon a normal balloon ( like ones bought for party’s) ?
It can be. The instructions are for how to build the hovercraft. What you’d like to test is totally up to you. You can try different balloons, different surfaces, different times of day for outside air temperature, etc. Just make sure you are only changing one thing at a time (one variable)!
As long as it’s smooth on the bottom surface it will work.
Just 1 question. What if the disc isn’t too old? Would the thing still move?
For this experiment is the floor the variable?
That’s a great question – I am not sure if they will be too big or not, so I would totally try it and see!
Would punch balloons work?
Do you mean like potholes?
No – you just need something to make a very small hole in the cap for the air to leak out.