At a firefighter's convention, a competition pits two contestants in mock combat. Each is armed with a

Question:

At a firefighter's convention, a competition pits two contestants in mock combat. Each is armed with a fire hose and a shield. The object is to push the opponent backward a certain distance with the spray. A choice of shields is offered. One shield is a flat garbage can lid; the other is a hemispherical lid that directs the water back toward the opponent. Which shield would you choose? Why?