The information below is subject to change as more event tips and details are included.  Please monitor this page regularly.

Event Description:

Before coming to the Physics Olympiad, participants build a water-balloon catcher and an adjustable-range catapult capable of hurling standard-size water balloons (about 3'' in diameter, 200g) distances between 20 - 50 feet over an obstacle of between 2 and 20 feet high.  During the competition two teams take aim at each other’s catapult.  A distance between 20-50 feet separates the catapults, and the obstacle is placed between them.  The operation of the catapult is triggered by one of the two students that comprise a team. The second student is tasked with defending the catapult with the water-balloon catcher and must stand no closer than 3 feet and no further than 6 feet from the catapult.  Balloons are launched simultaneously. The first team to successfully hit the other team’s catapult without having their own hit wins and moves on to the next round.  A hit is determined either by a direct strike on a catapult or when a balloon bursts in the process of defending the catapult.  If neither team scores a hit after six tries, each team gets a single chance at an undefended catapult and the one to strike nearest the other wins.

Event Location and Time:

Apparatus and Materials:

• Definition: a catapult is a device that uses stored mechanical energy to hurl a projectile a desired distance.  Firing of the projectile is actuated by a trigger mechanism.  Devices that use stored chemical, biological, electrical, magnetic, or other non-mechanical forms of energy are not be permitted to compete.
• The largest cross-sectional area of the water-balloon catcher must be less than 4 ft² and allow the defender to safely defend the catapult at a distance between 3 and 6 feet from the catapult.
• Once armed with a water balloon, the catapult must remain armed for a period of no less than 30 seconds, until a team member uses its trigger mechanism to initiate the launching of the water balloon.
• Each team will design, build, and bring its own catapult-catcher combination to the Olympiads.  All materials are allowed for construction consistent with the stated rules.
• Water balloons will be provided to each team.
• Team members must wear all protective gear (such as helmets, masks, etc.) provided to them by the judges during the competition.   Be prepared: students may get wet!

Event Rules:

• Every team must have two students.
• Before a catapult-catcher combination is used it will be inspected for compliance by the judges.
• Teams will be randomly assigned to each other in each elimination-round.  In each round, the distance between catapults and the height of the barrier will be adjusted by our judges within the parameters listed in the event description.
• In each round, both students will prepare, aim, and arm each catapult with one water balloon at a time in the allotted time (maximum 2 minutes, including adjustment for a different range).
• A student will trigger the operation of a catapult ONLY WHEN and WHERE instructed by the judges.  No practice launches are allowed at the Olympiads.
• Once the judges authorize a launch, one student from each team must launch his/her catapult within 15 seconds.
• The other student can try to catch the balloons using the balloon catcher in the designated target area.
• If a balloon bursts while attempting to be caught or strikes the catapult, then the team is hit.  Up to six attempts will be made to hit the other team’s catapult. The first team to be hit without hitting the other will move on to the next round, eliminating the other. 
• If neither team is hit, the tie-breaker will be determined by the closest of a single additional attempt (without defense).  In the even that both teams score a direct hit in the tie-breaker, both team’s are eliminated!

 Judging Criteria:

• The Gold medals will be awarded to the winner of the final round.  The Silver medal will be awarded to the team eliminated from the final round.  Bronze medals will go to the two teams that are eliminated from the semi-finals round.
• All decisions will be determined by judges and are final.

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The University of Michigan Physics Olympiad has no connection, association, or implied authorization by the USOC, the IOC, or the IPC.
Revised: March 08, 2008.