Mechanical Engineering student David Cuff gives his team’s robot, “Spare-Parts Steve,” a boost during a ski race in the Union ballroom Monday.

With more than 100 U students and a few hundred other participants, the U department of mechanical engineering hosted the sixth annual Design Day in the Union ballroom on Monday.

The activities began at 9:30 a.m., when teams of junior high students tested catapults they built by flinging Brigham Young University cougars to see whose would go farthest.

First-year mechanical engineering students engaged in an event titled, “Free Willy III,” in which teams competed to see who could get more oil out of the top of a tub, as oil spills are a major source of pollution with expensive cleanup costs associated.

Brett Verhoef, a mechanical engineering senior at the U, and other third-year students participated in an event titled, “Robot Skiing.”

After two semesters of training, they built autonomous skiing robots that raced against each other, said Roy Merrell, U master’s student and teaching assistant for mechanical engineering 3200.