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Solar Car by Isaac and Anjali

We live in sunny California. We know that people are using the sun to provide energy to businesses and homes. Isaac even has a toy solar car. Our question: How does the sun's position in the sky affect a solar car's performance?

What did we do?
We decided to measure the speed of the solar car at different times of day, when the sun was at different points in the sky. We marked off a distance of 40 feet on a flat, level sidewalk and recorded the time it took the car to travel the distance. We took the average time for two trials, every hour from 8:00 a.m. to noon. We also measured the sun's angle each time we did a speed trial. We tied a string to the top of a tall stick. I held the stick straight up on the sidewalk and Isaac pulled the string tight until it touched the end of the stick's shadow. He measured the angle of the string using a protractor.

What did we find out?
As we hypothesized, the car received more energy from the sun as the sun moved higher in the sky. The car's solar panels faced straight up, so when the sun got higher in the sky they had more light shining on them. When we examined our data, we were surprised to see that by 10 a.m. the car was already reaching its top speed, even though the sun hadn't reached its highest position in the sky yet.

What can you do?
• Track shadows throughout the day. Each hour, put a marker at the end of the shadow from a small tree or just a stick in the ground. What do you notice about the markers? Do they form a curve or a straight line? What time of day is the shadow shortest?

• Do you have a solar toy car? Can you tilt the solar panels toward the sun? Try measuring the car's speed early in the morning, pointing the panel toward the sun. Can you increase the car's speed this way?

• Use this technology investigation as a science fair project idea for your elementary or middle school science fair! Then tell us about it!

 SciLinks More on Solar Cells Go to the DFTV Boards, and tell us about your science investigation.