The perfect rainy-day science activity for kids is a good old-fashioned paper airplane challenge.

Building and launching paper airplanes is one of the easiest, no-cost STEM activities out there. All you need is a few sheets of paper and enough space to launch the paper aircraft.

Experimenting with different paper airplane designs helps kids develop engineering skills. Each airplane design is going to perform differently and some will fail. In the end, kids will walk away with a better understanding of how aerodynamics work … perhaps without even realizing it!

How to talk to your kids about the science of flight

It’s fascinating and mysterious for the smallest child to watch the creatures and machines take to the sky. Even with variations like perfected throwing technique, fans and higher launching points, paper airplanes perform differently depending on their design. Design ties into the physics of flight.

First, it’s important to understand there are four forces of flight: thrust, lift, drag and weight. These four forces affect all instruments of flight, including jets, gliders, paper airplanes … even birds. Teach the lesson on a paper airplane at home, and the science of what keeps the plane in the air will make much more sense.

Thrust is the thing that sends the plane into motion. A jet’s thrust comes from the engine. A glider’s thrust comes from a running leap off a cliff or hilltop. A paper airplane’s thrust comes from the throw.

Lift is that force of air that keeps the plane aloft. Ever stick your hand out the window of a car speeding down the road? You can just feel that muscle of air pushing up on your hand and forearm. That explains the purpose of wings — the lift pushes up onto the wings and keeps the plane in the air.

Drag is the force of air that is moving in the opposite direction of the flying object, and slows it down. If you’ve ever ridden a bicycle into a strong headwind, you know all about drag.

Weight is the force of gravity, which is always pulling the plane back to Earth.

In other words, there are two things that make the plane go and fly — thrust and lift. And two things that make the plane slow and fall — drag and weight.

What it comes down to is making the paper airplane “go and fly” for as long and as far as possible, before the “slow and fall” overtake it.

For more ideas, the Smithsonian National Air and Space Museum website has a ton of helpful, interactive features and videos.

Building a paper airplane

Getting started on your paper airplane challenge is as simple as hopping online and printing off some of these templates and instructions. There are many to choose from, but the best two to start with are the classic dart and the condor. Both are simple and well suited for beginners and they fly very well. As the folding gets easier, test out one of the advanced designs — including the helicopter.

By the way, you can even build a replica of the far-gliding paper airplane that made it into the Guinness Book of World Records.

Launching the experiments

Once the planes are made, ask the kids to predict which plane will fly farthest and fastest and see if they can explain why. What’s in the design that would help this plane go fast or fly far?

Then, fly the planes and note your observations. If you like, you can try some of these variations:

* Fold planes from different kinds of paper. Does a construction paper plane fly differently than one made from office paper?

* Try different sizes of planes. Do smaller planes fly farther or faster than large ones?

* Experiment by adding weight. What happens when you tape coins or attach paper clips on each wing? What happens if you add weight to the front of the plane? How about the rear?

* Try whatever fun variations come to mind. What happens when you add, say, a box fan to the “run?”

* Afterward, read all about it! Head to your local library and check out a few books about planes and famous aviators, like the Wright brothers and Amelia Earhart.

Remember, anyone who has been a maker has stories to tell about failure. It will likely take repeated tries before they find the model that works. Be sure to praise them not for the distance flown, but for the effort and willingness to continue.