POCATELLO - Sometimes, you have to break a few pumpkins to make a trebuchet work right. Students from three area high schools who participated in an annual tradition called the Pumpkin Chuck Saturday afternoon will attest to that fact.

For several years, Snake River High School hosted the physics competition, in which students from competing high schools design and build 13th century war weapons to hurl pumpkins as far and accurately as possible. After funding cuts forced Snake River to give up the event, Idaho State University's physics club took up the cause this year.

In addition to the physics club members, teams from Malad, West Side and Blackfoot high schools competed in a field at the Pocatello Regional Airport.

"This is something many high schools looked forward to for so many years, and it would be a shame to let it die," said ISU physics professor Phil Cole.

The Malad and Blackfoot students constructed towering, mostly wooden structures called trebuchets - unlike catapults, which utilize tension to make an object fly, trebuchets derive their energy from falling weight.

On Malad's first attempt, the device's arm flew forward after the release pin was pulled, but the pumpkin was lofted high into the air about 10 meters in the wrong direction.

Cole explained the sling was too short, and the students made the necessary adjustments. On the next launch, the arm tossed the team's pumpkin on a high arc, and a small crowd cheered as the gourd smashed into bits 42.8 meters away.

"It's working very good for what we thought," said Cort Thorpe, a junior in the Malad physics class. "It didn't break. That's what we were hoping for."

The Malad students each built miniature trebuchets and took the best ideas from them all to develop their entry. They received some funding for their project from their school and local businesses - team member Chris Hess secured building materials from his family's business, Hess Lumber in Malad.

The Blackfoot students starting planning for the competition at the beginning of the school year - they used a design a classmate had scrawled onto a piece of paper - and they commenced construction about a month ago. It took six strong men to pull the arm of the Blackfoot machine to the ground; the people who pulled the release pin wore motorcycle helmets for safety. However, both of Blackfoot's first two distance launches hurled pumpkins straight into the ground.

ISU physics Professor Steve Shropshire, adviser of the physics club, was optimistic about the Blackfoot class's potential despite the early setbacks.

"Blackfoot, their machine has promise if they could get (the pumpkin) out of the sling," Shropshire said, adding he liked the long length of the machine's arm.

His thoughts turned out to be prophetic. Though Malad won the trophy for longest throw with a distance of 51.43 meters, the Blackfoot machine came in second with a throw of 40 meters. However, Blackfoot's trebuchet launched a gourd 74 meters during a throw that didn't count because it was intended to measure accuracy.

West Side finished first for accuracy using a catapult made from a boat trailer. The West Side machine launched a gourd to within 1.4 meters of a designated target.

"There's a lot of brilliant physics in these things. They're really fun," Cole said of the devices used in the competition.

Shropshire added, "It gives the students a good opportunity to learn some applied science, some applied physics and some physics principles."

The cost of the event was covered by a combination of entry fees from the high school teams, funding from the Associated Students of ISU and proceeds from an ISU physics club fundraiser.

The physics club didn't compete officially against the high school teams, but those who witnessed a demonstration from the club's machine were treated to an impressive display. It launched a pumpkin 190 meters.