# Fast and Easy Science Fair Projects: A Lopsided Pinwheel

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Scissors
Cardboard box, standing at least foot high
Piece of thin cardboard, oak tag, or standard size construction paper
A push-pin
Metal washer
Pencil

## Balancing points of oddly shaped objects

Purpose: How to discover the balancing point of irregularity shaped objects.

Overview: The balancing point of a square or circle is easy to find. You must need to measure. It's right ar the center of it, as long as the object is basically two-dimensional or flat; that is, doesn't have a significant amount of depth (a rock or glob of clay is definitely third-dimensional).

The balancing point, however is not always in the center. It's the point at which, if an axle is placed through it, an object can be spun like a wheel and it will stop at a different spot every time. Is it possible to find the balancing point of something flat, but that has an odd unsymmetrical shape?

Hypothesis: Hypothesize that you can find the balancing point of an irregularly shaped piece of stiff paper or cardboard.

You need:

• A push-pin
• Piece of thin cardboard, oak tag, or standard size construction paper
• Cardboard box, standing at least a foot high
• Scissors
• Metal washer
• Pencil

Procedure: Draw an irregular shape on a piece of thin cardboard, oak tag, or constuction paper and cut it out with scissors. You may draw something like the six-sided shape shown here. Although the cut-out shape will be really three-dimensional (it has some depth, or thickness, as well as length and width), for the purposes of our project, this third dimension is so small we can assume it will not affect the results.

Set a cardboard box on the table. Near one edge at the top of your shape, place a push-pin through your object and into the edge of the cardboard box, you can use a cork bulletin board or a piece of plywood, as long as it is kept perpendicular to the ground (standing up straight). Do not push the pin in all the way. Swing the object back and forth to be sure it can move freely.

Tie one end of a piece of thread onto the push-pin and tie a metal washer, use any object as a weight to cause the string to hang straight down (a large paper clip, for example). We are going to use gravity to make sure the line we draw will be perpendicular (at a 90-degree angle) to the ground. The thread must also hang straight down and be hanging freely, not hung upon any-thing. With a pencil, draw a line tracing the path of the string across the object.

Next, take out the push-pin, turn the object about 90 degrees (it does not have to be turned an exact amount), and push the push-pin into a point near the top edge and through to the cardboard box. Again, hang a thread from the push-pin and draw a line tracing the path of the string as it falls across the surface of the object. The shape of the pbject is our Variable; gravity and the line with the washer hanging down are Constant.

Where the two lines intersect (where they cross) is the balancing point of the shape. How do you do this?

First you can verify it by turning the object once again and repeating the hanging of the thread from the push-pin, drawing a third line. That line, too, should cross at the sams spot where the other two meet. Other similar lines will also cross there.

Second, prove that this is the balancing point by pushing a push-pin through that intersecting point and into a stick, making a pinwheel-like toy. Give the object a sin a number of times. Each time it should stop at a different point.

Results and Conclusion: Write down the results of your experiment. Come to a conclusion as to whether or not your hypothesis was correct.

Something more: 1. Place numbers all around the edges of your shape to make a spinning "fortune wheel" game (in this case "Hexagon of Fortune"). You and your friends can guess what number it will stop on when given a good spin. Try turning your object into a pinwheel by bending up some of the edges to catch the wind.

2. Draw and cut out more objects, each with a different number of slides or some irregular shapes. Find the balancing point of each object and prove it. Or you and your friends can guess where the balancing points will be and find out, using methods above, which comes closest.