What class of lever is a mouse trap?

A snap-back mousetrap is both a second-class lever and a third-class lever. When the mousetrap is set, it is a second-class lever because the load of the force rests in the spring. When the spring is released, the force load is on the arm, which is a third-class lever.

When the mousetrap releases the arm, the spring becomes the force that snaps the arm. When the arm is set downward to coil the spring, the force of the arm loads the spring. The locations of the fulcrum, load force and effort force determine the three classes of levers. Levers are simple machines that make work easier to accomplish.