By: Beth Post

Free Saturday at Explorit

Public free to explore the joys of toys

Tomorrow, August 22, entrance to Explorit Science Center will be free to the public from 11:00 a.m. to 4:30 p.m. Come explore the current exhibition, The Way the Ball Bounces: The Science of Toys and Games. Then visit the Discovery Den, where you can check out any one of several science activities or examine the microscopic creatures to be found in water from Putah Creek. Follow that up with a turn at the probe microscope, with which you can examine in microscopic detail the cloth of your shirt or the hair on your arm. You're sure to find plenty to do and experience at Explorit this weekend.

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Mark your calendars! Explorit announces the grand opening of its new West Wing, to be held 1:00 to 4:30pm on Sunday, September 20th. The West Wing is Explorit's newest expansion, a 1,200 square foot space that provides greatly needed classroom space for programs and office space for program staff. Expansion was made possible by the Evelyn Buddenhagen Space Fund, the generous participation of the Davis community at the 1996 Dinner at the Dump and the contributions of regional businesses.

The Grand Opening will be free to the general public and will include fun-filled science activities such as a chemistry show, story telling by Explorit educators and carnival games. So don't miss the Grand Opening; it's sure to be a great science event to wrap up the summer season!

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Speaking of carnivals, the California State Fair opens this weekend in Sacramento. What would a state fair be without a huge midway, filled with rides? And, of course, the most popular rides are usually roller coasters - the "scream machines."

Much has been written about the science of roller coasters. The focus is often on the forces of motion exploited in getting coasters up and down hills and through loops, and the resulting gravitational forces experienced by the rider. It's those "g" forces that bring out the screams in the scream machine! There are also other, very basic forces at work in getting a roller coaster to roll, and, perhaps as important, in getting it to stop.

The simple fact is, a roller coaster at the top of its run has all the energy required for the run stored as potential energy (PE). Once the coaster starts to roll, PE is converted to KE, or kinetic energy (motion), and friction. It is friction that determines how steep the first hill must be before the coaster begins to roll, and friction that causes the coaster to "lose energy" or momentum and eventually stop.

Friction between any two surfaces is measured as the ratio of the forces required to move a rolling object along a surface to the forces holding the two surfaces together. The resulting number of such a calculation is called the coefficient of friction. Ball bearings rolling on a bearing face have a coefficient of about 0.002, meaning friction is relatively low. The wheels of a roller coaster against its track exhibit various coefficients of friction throughout a run; braking increases the coefficient at various turns and, of course, at the end of the run.

If you are lucky enough to get to the fair and take a rollicking ride on a roller coaster, try to observe where the coaster experiences the greatest amount of friction. What do the wheels and track look like? When are brakes employed (besides at the end of the ride!)? You may find it's fun keeping "track" of science at the fair!

After taking your roller coaster ride (or instead of it!), come to Explorit's current exhibition, The Way the Ball Bounces, and test out some of the basic principles of roller coaster physics. You can design your own coaster track for Hot Wheels, and test it out for speed and safety. Try running different cars on the track, to see the effect of friction on objects of different weight and wheel size. Who knows - maybe you'll design a future state fair roller coaster track!

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Explorit Science Center is located at 3141 5th Street in East Davis. The current exhibition is The Way the Ball Bounces: The Science of Toys and Games. Public hours are Saturday from 11:00 a.m. to 4:30 p.m., Sunday from 1:00 to 4:30 p.m., and Tuesday through Friday from 2:00 to 4:30 p.m. Regular admission is $3; members, teachers (with school ID) and children under 4 are free. For more information, visit Explorit's web site at www.dcn.davis.ca.us/GO/EXPLORIT/ or call Explorit at (530) 756-0191.