If your child is interested in learning more about how planes move, you could have a future scientist or engineer in the family. Nurture this interest with trips to a science center and with enjoyable activities that help your child understand propulsion.
Your child make a balloon race across a string. She'll need two balloons, 8 feet of string, a clothespin, a straw, scissors and two pieces of tape. Cut a fourth of the straw off and put it part way up the neck of a balloon. Use tape to secure the straw by taping the neck tightly around it. Thread the string through the straw and secure the ends of the string to two chairs or other pieces of moveable furniture. She'll want the string to be as tight as possible. Blow up the second balloon until it's face-sized, twist the end and use the clothespin to clip it shut. Tape the balloon under the straw, with the clothespin facing away from the length of string. If she wants, she can tape a picture of a rocket or airplane on the side of the balloon. Now let her take the clothespin off. For fun, measure how far the balloon went. She can try it again but with the balloon that has the straw in it. Have her compare results.
Swimming provides a simple way to experiment with propulsion. Haul your little scientist off to the beach or a pool and challenge him to find the best way to swim. Explain that kicking and moving through the water is also a form of propulsion. Bring a stopwatch so you can time his laps as he tries everything from the front crawl to the doggy paddle or backstroke. After he's finished, compare the times. Ask him which strokes were the hardest or most tiring. Get him thinking about the economy of movement, after all, if he's too tired to move after choosing the fastest stroke, isn't it a slower swim style better?
The Spinning Blimp
Your child can design her own blimp using paper, scissors, a ruler and markers. She should cut a strip of paper so it's about a half inch wide and between 6 and 8 inches long. She then should make a cut partway across the strip at one end and then turn it around and do the same thing -- the cuts are on opposite sides at opposite ends. Those cuts let her join the ends by slipping one cut into the other, leaving it looking almost like a little fish. Now she can hold it over her head, drop and watch it spin. The blimp spins best when it's held with an edge of the strip pointing up, like a fish swimming on its side. She can experiment with the blimp by trying different types of paper, longer paper or making the cuts in different places. Get her to spin it faster or try throwing it up higher first.
Help your child build his own rocket ship with a pencil, paper, scissors, a straw and tape. Roll paper around the pencil and cut it so it's only a little wider than the pencil. He can remove it at this point to color it if he wants, wrapping it around the pencil again when he's finish. Tape the paper with a long piece of tape down the side. You don't want air to leak out of the side later so ensure that it doesn't have any holes. Next, your child should tape one end of his rocket shut, preferable in a point, but it can be fun to experiment with different fronts such as flat and crumbled. Slip the pencil out and his rocket is almost ready. All he has to do is put the rocket over a straw and blow into the end of the straw.