I've finally enrolled in a Human-Computer interaction course and am reading Donald Norman's The Design of Everyday Things.
Below, I've attempted to brainstorm my own real-life examples to demonstrate his basic concepts.
Affordances and Signifiers: The corner of my Rubbermaid food container lid affords pulling. The tab-like design is an example of a real affordance because it allows the user to physically pull the lid to open the container and access the foods inside. The corner of this lid is also a perceived affordance as an easily discoverable signifier of that affordance of pulling.
Feedback: An old Metro bus farebox exemplifies bad feedback in design. I struggled with this because there was no indicator/feedback signalling that I put in the right amount of change for the zone I was in or the time I was boarding the bus. What if I was boarding at my watch-declared 6:29pm, but it was actually 6:30pm, when the fare is discounted? When is the "start of service" if I'm taking the bus at 3 or 4am? What are Metro holidays that merit discounted fares? Do Columbus Day or MLK Day count? As such, I never knew when it was acceptable to walk away from the bus operator after depositing my change.
I think newer fareboxes do give feedback when the proper change is added either via a data screen or buzzing sound. I'm sure that having a feedback system delivered via multiple modalities (sound, visual) makes for a better user experience for the fare-conscious like me.
Constraints: The Presidential nuclear briefcase (or also known as nuclear football), is a prime example of both a physical and semantic limitation to nuclear warfare. If Trump decides to preemptively launch a nuclear strike, he must (1) verify his identity to the Pentagon with a "biscuit," (2) specify the type of attack (out of 800 warheads) he wants to deliver, then (3) allow 15+ minutes for Strategic Command's launch officers to gather their collective conscience to launch the missile (the process of which also contains its own checks and balances).
This whole process is a physical constraint to launching a nuclear attack, whether by design or logistical bureaucratic necessity. Trump must open the briefcase, read through the instructions, contact Pentagon, choose a warhead, and wait for the order to be executed. Semantically, I wouldn't be surprised if plenty of "CAUTION" warnings were stated in the instructions.
Visibility of System State: This is demonstrated by my water heater/boiler. An activated light corresponds to the temperature that the appliance is keeping the water. The light is a persistent characteristic that helps to form people's conceptual models of how a water heater/boiler functions. When I look at my heater/boiler in the image below, I know that the device is on and that the water is being kept at 180-degrees Fahrenheit.
Conceptual Models: An oven is being used as a storage cabinet for pots, pans, and various other dishes and appliances. This oven is an example of how the mental model of the oven designer did not align with the mental model of the user. This user probably does not know what an oven is and implied from the shelving racks that it is a cabinet meant for storage, especially for metal and other heavy-duty objects.
This scenario might also demonstrate the oven as an accidental affordance, where the user uses it opportunistically as storage space.