Launch “Magic” Balloons
In this science experiment, kids experiment with balloons and moving air to explore forces and the principles of flight.
Simple explanation: The air pressure inside the column of blowing air is lower than the still air outside, which causes the outside air to press in. This helps to hold the balloons inside the column of air -- kind of like an air hug! This is Bernoulli's Principle. Round objects work best because they allow the air to flow smoothly around them, keeping the forces constant.
Detailed explanation: When air moves quickly over an object, it lowers the air pressure. This concept is called Bernoulli’s Principle, after Daniel Bernoulli, who first discovered that as the speed of air increases, pressure decreases.
Airplane wings and helicopter blades are designed to take advantage of Bernoulli’s Principle. When air moves quickly over the wing or blade, the air pressure under the wing is higher, which pushes it up, creating lift.
Kids love this activity, and can play with the balloons for hours. This is also a great activity to use at fairs or festivals. If you run a science business, you can print your website or other information on the balloons and hand them out for the kids to take home.
Safety Notes
Be sure children cannot get their fingers close to the fan blades.
Materials
- Balloons - 3+ per class
- Fan that can be tilted to blow upwards - 1 per class
Instructions
Inflate the balloons and tie them off. Have kids toss the balloons in the air and observe what happens. Now have them try it again, and try to keep the balloon in the air by blowing. Can they do it?
Now turn on the fan, starting with the lowest setting, and aim it to the ceiling. Be sure it is aimed straight up.
Put one balloon into the column of air coming from the fan. The balloon should bob around but not blow away (though the balloons will eventually get pushed out of the air stream). What is happening here? Show the kids that if you use something that's not round, like a crumpled piece of paper, it goes flying away.
Now try adding another balloon, then try a third. Why don't they blow away? What force is keeping the balloons swirling around? This is Bernouill's Principle!
Allow the children to experiment with the balloons, placing them lower in the air stream, or higher, or on the edge. What do they observe? What happens when you increase the speed on the fan?
For younger scientists, consider using a Sharpie to draw a face on each balloon.
Also consider using ribbon to make legs that can be taped on -- just don't add too much weight. Note that using ribbon will decrease the ability of the balloon to stay in the column of air, and thus reduce the ability of the children to fully experience and observe the science. You may want to make just one balloon like this just for the kids to play with once the experiment with the smooth balloons is finished.
This experiment also works well with inflated, lightweight balls, such as beach balls.
You can try this experiment with a powerful hairdryer and balloons or a tennis ball. And you can buy toys that use a ping-pong type of ball and a pipe to let kids create the stream of air themselves.
You may also want to try the make paper airplanes activity.
Please leave comments about any variations on this experiment that you've tried in the comments section below!
