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The great pumpkin launch

Whitworth College physics students prepare their trebuchet that will launch a pumpkin. 
 (Brian Plonka photos/ / The Spokesman-Review)
Whitworth College physics students prepare their trebuchet that will launch a pumpkin. (Brian Plonka photos/ / The Spokesman-Review)

Not for an A or for a cash prize or even a fancy periodic table. Four Whitworth College science seniors did it all for the honor of building the school’s most worthy trebuchet. And their extensive Internet research and 30 hours of work paid off.

“The winning team just did it for fun, so all they get is glory and honor,” said the organizer of the Whitworth’s first pumpkin launch contest, assistant physics professor John Larkin.

At the beginning of the year, students were invited to enter the contest to create a pumpkin-throwing machine (no gunpowder allowed). The design that threw the farthest would win.

Seven groups entered. Each opted to make a catapult or a trebuchet – essentially medieval weapons of mass destruction. Some did it for a class project; others entered to challenge their brains.

(So what’s the difference between a catapult and trebuchet? Think back to a grade-school food fight. When you loaded a spoon with pudding and pulled back the spoon with your finger and made the food fly across the lunchroom by releasing your finger – that was a catapult. If, however, you filled the spoon with pudding, laid the spoon across a finger like a teeter-totter and dropped your fist onto the spoon’s handle – that was a trebuchet.)

The greatest throw at Sunday’s competition belonged to the group that included Will Clegern and John Lesch. On Friday, the best teams gave an encore performance to about 60 students who huddled at dusk on the woodsy campus to watch bowling-ball-size pumpkins fly the length of a football field.

“This is for bragging rights,” Clegern said.

His team counted down from three and with a “Let ‘er go!” released the rope that was holding 800 pounds of concrete suspended.

The force of the falling concrete propelled the pumpkin (or in physics terms, the potential energy of the concrete was converted to the kinetic energy of the pumpkin) until the fruit exploded into a tree some 300 feet from the start of its flight. On its next demonstration throw, however, the arm got caught and snapped the trebuchet in half.

Some groups used water as weight. Others used garage-door springs instead of weight. Only one of the seven groups used a catapult, which shot an underwhelming negative 11 feet because of a malfunction.

But that was OK with Larkin.

“Even the failures were a learning experience,” he said.

Students said the value of the project wasn’t learning concepts and equations (they already understood most of that). The value was putting the concepts into practice.

“I don’t know that we learned a whole lot,” Clegern said. “We got to apply what we learned in class.”

The winning team calculated that in perfect conditions its machine could toss a pumpkin 400 feet.

“So we figured we could throw 300 feet with friction and air and everything that could go wrong,” Lesch said.

On their best throw during Sunday’s competition, the pumpkin reached 290 feet before hitting a tree.

As for the winning trebuchet that was damaged on Friday, Lesch and Clegern vow to rebuild. They’ve made sure their device will fit on the back of a pickup for easy transport.

“If a snowman lands on your roof …,” Clegern warns.

“… It wasn’t us,” Lesch interrupted.


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