Door Knobs and Handles

A classroom door knob or handle demonstrates the lever principle. When force is applied to the handle or knob, it rotates the central spindle (fulcrum), which retracts the latch (load), allowing the door to open with minimal effort.

1. Identify the fulcrum: Show students that the spindle inside the door knob/handle acts as the pivot point.
2. Apply effort: Push down on the lever handle or twist the knob.
3. Show the load: Explain that the latch is the part resisting movement.
4. Retract the latch: Demonstrate how turning the spindle retracts the latch bolt from the strike plate.
5. Open the door: With the latch retracted, push or pull the door to open it.
6. Review the parts of the lever: Effort (your hand force), Fulcrum (spindle), and Load (latch mechanism).

• None available

• Compare a lever-style handle to a round knob, showing differences in motion (push/pull vs. twist).
• Demonstrate how a classroom lock allows the key to control the lever, adding a real-world application.
• Ask students to think of other levers in daily life (scissors, bottle openers, pliers).

• Ensure the door or demonstration setup is stable and won’t tip over.
• Supervise younger students to prevent pinched fingers in the latch mechanism.

• How does the handle make it easier to retract the latch compared to pushing directly on the latch? (The handle provides leverage, spreading force over distance.)
• Why is a lever handle easier for some people to use than a round knob? (Less grip strength is required to push a lever compared to twisting a knob.)
• What are the effort, fulcrum, and load in this demonstration? (Effort = hand force, Fulcrum = spindle, Load = latch mechanism.)