Masters of 'spring' theory

Physics teachers embrace a new method.

Posted: August 03, 2007

The task was immense. Several 10-foot-long springs swung from the room's second-story balcony. On the dangling end of each hung a 500-gram weight. A swarm of physics teachers hustled about, calculating elastic forces and measuring displacements with meter sticks.

Their goal was to drop this weight from a carefully determined height so that it would just kiss an egg on the ground. If the egg broke . . . well, wrong answer. But if the egg remained intact, they could brag about having mastered a new kind of physics lesson.

The teachers were learning modeling, a revolutionary way to teach physics that already has reached 7 to 8 percent of physics teachers in the United States. For three weeks last month, the East Coast Modeling Workshop at Ridley High School brought modeling training to more than two dozen Philadelphia-area teachers.

Students of modeling discover physics concepts for themselves, like young Galileos, by playing with gadgets. The teacher's job is not to stand before students and instruct, but to inspire conversations about physics and keep common fallacies at bay.

"It's very promising, I think," said Robert Fuller, professor emeritus of physics and former leader of the Research in Physics Education Group at the University of Nebraska. "There's tons of evidence that these indirect things . . . are more effective."

Modeling is a departure from the traditional method, often referred to in physics circles as "plug and chug." That is, solving problems by plugging numbers into memorized equations - F = ma, F = mg, F = kx, and so on - then chugging through the math.

In traditional physics, students are expected to memorize the equations before they really understand their meaning - that force, for example, is equal to mass multiplied by acceleration. Conversely, the physicists who developed the formulas figured them out by observing the world. Basically, they used modeling.

"Newton didn't have a textbook. Galileo didn't have a textbook," said teacher Jess Dykes, who has used modeling for three years at Ridley High.

On a standardized physics test developed to assess comprehension, students of the traditional method averaged 42 percent. Modelers averaged 69 percent.

Teachers are often surprised to learn that their students bomb this test, said Doug Vallette, a 10-year physics modeler at Unionville High School. When the test first came into use in 1992, it was a revelation for teachers: Physics instruction didn't work.

In the early 1980s, Arizona State University professor David Hestenes, a theoretical physicist, decided that physics should be taught as it is done, through scientific models. This led to his development of modeling.

Over the years, modeling has spread at Arizona State, where Vallette and Dykes, leaders of the three-week Ridley workshop, learned it. The workshop was the first in the Philadelphia region.

According to Fuller, modeling's main drawback is that you have to take these intensive sessions to teach the course.

Students appear to appreciate the effort.

"The more I incorporated this technology, the more I broke down barriers," said Arthur Zadrozny, modeler at Kennett High School. "I had kids tell me at the end of the year how it made them less scared."

Ron Smith, a physics teacher at William Allen Senior High School in Allentown, sees modeling as potentially useful at his distressed school, which failed to meet its threshold on its latest Pennsylvania System of School Assessment. The first PSSA science section will hit schools next spring and includes physics questions.

"We have a 20 percent dropout rate," Smith said, but modeling might give students a reason to stay with the program. Also, because many of his students speak English as a second language, the action-oriented approach has "tremendous potential," Smith said.

Modeling can be used to teach other sciences, too. "It's a method, not a curriculum," Dykes said.

Embedded in the approach is the learning cycle. In physics, the first step is to give the students some simple objects - perhaps a spring and some weights. But there's no assignment. Instead, teachers ask students questions about the weights and objects to get them thinking about how the world works.

In a process that mirrors scientific experimentation, the students use the equipment to collect data. In the spring-and-weight example, the students observe that the force of gravity has a greater effect on the spring as they burden it with heavier weights.

In the cycle's dramatic conclusion, the students must accomplish some illustrative task to cement their new physics knowledge.

Like grazing an egg - but not breaking it - with a weight suspended from a spring two stories high.

When the final team went to take a crack at the egg, tension was high. No one had successfully completed the task. As the last weight fell, the spring stretched and stretched and stopped. At that moment, and to the delight of the teachers, the egg and weight kissed.

The laws of physics worked.

Contact staff writer Erika Gebel at 215-854-2999 or

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