The Science of Flying

“What makes aeroplanes fly?” asked C(10) a few weeks ago. We’ve had fun finding out.

An aircraft flying in steady forward motion is subject to four forces:  thrust, drag, lift and weight.  Aviation for Kids: A Mini Course For Students in Grades 2-5 (free online) contains dozens of ideas for experimenting with these forces.

Thrust

Thrust is the force that moves a plane forward through the air. To investigate thrust, we made three different “aircraft”, each powered by a different thrust mechanism.

1. Elastic band thrust

First, we made elastic band-powered planes. We experimented with thrust by observing the distance our planes flew when we changed how far we pulled our elastic bands before we released them. {Instructions are on p3 of Aviation for Kids.}

In real aircraft, of course, thrust is created by a jet engine or propeller.

2. Air pressure thrust (blowing through a straw)

Our second aircraft was powered by blowing through straws, one inside the other.  {For instructions see p7 of Aviation for Kids.}

We experimented with placing the wings at different points along the straw and observing the effect on our aeroplanes’ flight.

C(10) suggested a competition to knock down unifix cubes with the planes.  It was more difficult than she’d expected!

3. High air pressure thrust (balloon power)

We made a balloon-powered rocket when we learned about space travel last year. The kids were delighted to recreate it as part of our investigation into thrust and drag. {See p 10 of Aviation for Kids for instructions.}

Newton’s third law states that for every action, there is an equal and opposite reaction – as the balloon deflates, it whizzes along the wire. It’s very cool!

Drag

Next, we investigated drag – the air resistance that slows an aircraft as it moves forward. If drag is greater than thrust, the aircraft cannot move forward.

To see the effects of drag, we attached a foam plate to the front of our balloon aircraft.

When it was subject to the increased drag of the plate, the balloon only managed to travel halfway across the room before it ran out of air.

Apparently it was hilarious to lie underneath the wire as the balloon zoomed to a halt.

Lift

The other pair of forces that operate on an aircraft are lift and weight. Lift is provided by the airfoil shape of an aircraft’s wings.

If you look up how planes fly, you find many references to Bernoulli’s principle. But some scientists think that lift can be explained perfectly well by Newton’s laws – that aircraft are forced up by the vast amount of air that the wings throw down.

Bernoulli’s principle

Whatever role it plays in helping planes fly, Bernoulli’s principle is fun to demonstrate, partly because it’s counter-intuitive.  We demonstrated Bernoulli’s principle in two ways.

First we placed a sheet of paper between two books. We blew through the gap.

The children had predicted that the paper would lift up as they blew underneath it. Instead, the paper sagged down. Bernoulli’s principle says that within a stream of fluid (such as air), pressure goes down as speed of flow goes up.  So when we blew, the air pressure under the paper decreased and atmospheric pressure from above pushed the paper down.

We also demonstrated with ping pong balls and a hairdryer. J(8) especially liked this one as he got to use a gadget.

When the hairdryer blows fast-moving air between the ping pong balls, air pressure between the balls decreases. Atmospheric pressure outside the balls pushes them together. (This doesn’t happen when you aim directly at the ping pong balls, but J(8) had fun doing it anyway.)

How do wings produce lift?

Lift is created by the curved shape of an aeroplane’s wing. This “airfoil” shape causes air to move faster over the top of the wing than the bottom. When lift is greater than the weight of the plane, the plane will move upwards.

We made paper airfoils and attached them to thread (see p25 of Aviation for Kids).

When we ran with our airfoils, they moved up the thread.

The airfoil also lifts when you spin around very quickly. This one was repeated many times!

(Aviation for Kids also suggests pointing a hairdryer at the airfoil. We did this but found it difficult not to blow the paper wing directly up or down.)

Weight

To experiment with weight, we made the world’s best paper aeroplane. This plane has great lift!

Then we increased the plane’s weight by attaching paperclips. It was easy to see that the extra weight reduced the plane’s lift. One paperclip actually had a stabilising effect, making the plane easier to direct. Two or three clips seriously impacted our planes’ ability to stay in the air.

What next?

C(10) has been making notebook pages about the science of flying. She’s come up with lots more questions as she’s been writing!

Our science this month is going to focus around the exciting engineering box we’ve just received on loan from the James Dyson Foundation, but we’ll definitely be continuing with the science of flying after that.

Further resources on the science of flying

Up, Up and Away: The Science of Flight (favourite)

Flight aerodynamics video  Explains how the four forces of flight operate (turn up the volume to compensate for the narrator’s monotone)

Bernoulli’s paper airplane experiment

Airfoil lifting force misconception

BBC Bang Goes the Theory Bernoulli’s principle and wings

Science kids – Flight lesson plans

A physical description of flight; revisited Technical article on how aeroplanes actually generate lift, and the Newton v. Bernoulli debate

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26 thoughts on “The Science of Flying”

1. We love Physics here! What great projects and experiments. I love to see the smiles on the children s faces! Enjoy the weekend.

1. Thank you, Melissa! Have a great weekend, too.

2. This is fantastic!! On my list of things I want to do now.

1. Thank you Phyllis. I can’t believe we’ve done something you guys haven’t – that must be a first! 😀

3. Looks great! Can’t wait till I have some time to dig through all the resources you have here. We are planning to celebrate Engineers’ Week in March and some of these experiments will be on our list!

1. I love the idea of Engineers’ Week. We seem to be having an engineers’ quarter! I’ll look forward to reading about what you do!

4. This goes along perfectly with the paper airplanes we just built in conjunction with studying Leonardo da Vinci. I love they way you did a hands-on activity that corresponds to each of the principles.

1. Thank you, Julie. Ooh yes – da Vinci! What a great idea for a tie in…

5. Great stuff! I pinning it for when Firecracker gets an urge to study aviation

1. Thanks, Rebecca! LOl about Firecracker getting an urge … I have lots of stuff like that pinned too. And it does get used! 🙂

6. You guys have been busy! I really enjoy reading this post, and am bookmarking it for later when we study flight. I like how you’ve done experiments to explore the different aspects of flight. Putting the videos in is a really good idea. The children’s enthusiasm and enjoyment for learning are wonderful to see.

I also really like C(10)’s lapbook, and her methodical approach. It’s something I wish to see more of from my homeschool student!

1. Thank you so much, Hwee! The children did have a lot of fun doing this. Oh yes, and me too!

I will pass on your compliment to C(10) – methodical is not a word often used to describe members of our family, so she’ll be very chuffed! 😀

7. What a fun day of science! My son would love this! I am going o bookmark it for a later lesson.

Thanks for stopping by my blog. The room was a lot of hard work but I like how it looks now.

1. It was actually several fun days, Jen! I hope your son has fun with it one day!

8. Wow, this post is such a great resource! The kids look like they had a blast – such great learning 🙂

9. What a fantastic series of experiments! Love the logic and organization behind them–guided inquiry at its best! Of course, my *favorite* pic is of C(10) pulling it all together–with a package of blueberries nearby–too engaged in her work to stop for a snack! Can’t wait to try these experiments here–thank you for the wonderful resources!

1. LOL! Yep, she was very busy at work! Thanks for your lovely comment, Dana. 🙂
(Email on the way to you soon, btw!)

10. Starting a transport unit next week with my first graders. Will definitely be back to try out some of these ideas! Thanks for sharing at After School!

1. Ooh I bet your first graders will love a transport unit! Have fun and thanks for hosting the link up!