Friday, June 17, 2011

Reinvent the paper airplane

We are sure you would have made and flown a paper airplane someday. Did it fly the way you had wanted it to fly? If it didn't, what did you do to correct the flight? Well, lets go back to our science classes and try to decipher the code. Here's the interesting activity to make the perfect airplane:


Activity Objective:

To build different paper airplanes that can fly longest or highest or most elegantly

Learning objectives:

1.       Understand airplane design and its various components

2.       Explore different airplane designs and find their individual qualities

Material needed:

1.       Sheets of paper (preferably, used but unfolded ones)

2.       Scissors (if needed)

3.       Paper clips

Process:

Let the children make all kinds of designs they know of with sheets of paper. Encourage them to use different thicknesses of paper right from a newspaper to a standard A4 size paper to a chart paper. Let them make different sizes of airplanes. To add some flavor of interest, ask them to name their designs based on their flight patterns. Some common names could be fighter, glider, elegant, diver etc.

Hold competitions like highest, longest and most elegant flight.

Factors to be varied and studied:

1.       Paper thickness

2.       Size of the airplane

3.       Angle of the wings

4.       Tail direction (does it work like radar?)

5.       Launch speed

6.       Launch angle

7.       Weight on the nose, tail, wings (attach paper clips)

Some images of paper airplanes:

Here's a video of children enjoying the flights of their own paper planes:

Some of the excellent images that we found on the internet are reproduced (with their sources) here:

1. DC-3 of paper airplane (http://www.zurqui.com/crinfocus/paper/airplane.html)

Another great design we found goood to make is at http://seedsottawa.files.wordpress.com/2011/03/paper-airplane.jpg:



For some technical aspects of designing the right airplanes, lets look at an excellent discussion on aerodynamics at http://teacher.scholastic.com/paperairplane/airplane.htm.

Aerodynamics

What makes a paper airplane fly? Air — the stuff that's all around you. Hold your hand in front of your body with your palm facing sideways so that your thumb is on top and your little finger is facing the floor. Swing your hand back and forth. Do you feel the air? Now turn your palm so it is parallel to the ground and swing it back and forth again, like you're slicing it through the air. You can still feel the air, but your hand is able to move through it more smoothly than when your hand was turned up at a right angle.  How easily an airplane moves through the air, or its aerodynamics, is the first consideration in making an airplane fly for a long distance.

Drag & Gravity


Planes that push a lot of air, like your hand did when it was facing the side, are said to have a lot of "drag," or resistance, to moving through the air. If you want your plane to fly as far as possible, you want a plane with as little drag as possible. A second force that planes need to overcome is  "gravity." You need to keep your plane's weight to a minimum to help fight against gravity's pull to the ground.

Thrust & Lift


"Thrust" and "lift" are two other forces that help your plane make a long flight. Thrust is the forward movement of the plane. The initial thrust comes from the muscles of the "pilot" as the paper airplane is launched. After this, paper airplanes are really gliders, converting altitude to forward motion.

Lift comes when the air below the airplane wing is pushing up harder than the air above it is pushing down. It is this difference in pressure that enables the plane to fly. Pressure can be reduced on a wing's surface by making the air move over it more quickly. The wings of a plane are curved so that the air moves more quickly over the top of the wing, resulting in an upward push, or lift, on the wing.

The Four Forces in Balance


Long flights come when these four forces — drag, gravity, thrust, and lift — are balanced. Some planes (like darts) are meant to be thrown with a lot of force. Because darts don't have a lot of drag and lift, they depend on extra thrust to overcome gravity. Long distance fliers are often built with this same design. Planes that are built to spend a long time in the air usually have a lot of lift but little thrust. These planes fly a slow and gentle flight.

Look out for the next exciting post on Walk-along paper glider...

Friday, June 10, 2011

Making a parachute to save the egg!

On the first day of the unSCHOOL workshop at Sayaji Club, Indore, the children were given the task of making a parachute to land a raw egg safely on the ground from the first floor. The activity looks deceptively simple. But going by the fact that only one group out of seven managed to get it right the first time, you could give it a serious try at home! I borrowed the activity from a training workshop I had attended earlier by Yardstick. We added some bit of our wisdom to it this time.

Here's the activity in detail:

Activity Objective:
To build a parachute to land a raw egg safely on the ground from about 15 feet height (or higher)

Learning objectives:
  1. Understand air pressure and how it can be used while making a parachute
  2. Explore different parachute designs and find the most suitable one

Material needed:
  • Large polythene bag
  • Raw egg (or ripe tomato or any delicate object that may break on falling)
  • Thread
  • Cello-tape
  • Plastic disposable cup

Process:

A parachute works by increasing the surface area of an object so it has more contact with the wind, which decreases the speed of the object. 

Ask the children to make groups of 2-3, and think about any parachutes they had seen in actual or in pictures or movies. Then they should draw the picture of what they want to make.  They should discuss the size and shape of the polythene, length of thread and the height from which they will drop the parachute. They should also think about how the egg should be placed in the cup. Encourage them to experiment with various factors and not be afraid of breaking the egg.

Factors to be varied and studied:
  1. Changing the payload weight
  2. Lengthening or shortening the length of the suspension lines
  3. Changing the number of suspension lines
  4. Increasing or decreasing the radius of the parachute
  5. Cutting holes and/or slits in the parachute fabric
  6. Shape of the parachute fabric- square, circle
  7. Fabric- polythene, cloth (wet/ dry)
This is how it went!

Making the parachute together
Making the perfect parachute!


Tying up the threads
Waiting for the parachute drop

And here's how we broke 6 eggs before saving the 7th!




Further references:
1.       For some theory on parachutes: http://www.pcprg.com/sptp.htm
2.       To calculate the diameter of the parachute needed: http://celtickane.com/projects/rocketry/project-i-a-successful-parachute/math-and-theory/