In this question, we are examining how to use a lever efficiently to lift a heavy metal beam. The use of levers is an application of the principles of mechanical advantage. There are three classes of levers, and the principle for all is the same: to use a smaller force to lift a heavier load.

The force or effort required to lift the load on a lever depends on the position of the fulcrum relative to the point where the effort is applied and the load.

1. Concept of leverage: The mechanical advantage is achieved by increasing the length of the lever arm where the effort is applied. The longer the distance from the fulcrum to the point where the effort is applied, the less force is needed to lift the load.
2. Optimal Fulcrum Position: Placing the fulcrum closer to the load increases the lever arm length on the effort side, which reduces the effort required to lift the load. This is because the effort arm (distance from fulcrum to point where effort is applied) becomes longer relative to the load arm (distance from fulcrum to point where load is applied).
3. Evaluation of Options:
   • Placing the fulcrum at the center of the plank would not provide significant leverage for either side, making the effort equally balanced but not minimized.
   • Moving the fulcrum closer to the worker decreases the length of the effort arm, requiring more effort to lift the beam.
   • Keeping the fulcrum fixed gives no flexibility to optimize the effort needed.
   • Moving the fulcrum closer to the beam increases the effort arm, providing maximum leverage and requiring less effort to lift the beam, which is the correct approach.

Thus, the optimal solution is to move the fulcrum closer to the beam. This adjustment increases mechanical advantage, reducing the effort needed. Therefore, the correct answer is to Move the fulcrum closer to the beam.