Form Follows Function
I recently had a cup of coffee using a cup that provided some discomfort to what is often the most soothing event of the day.
Referring to the drawings above, the loop for the finger was only large enough to allow the index finger (A). The weight of the coffee, being offset from its support at (A) is pulled by gravity and rotates around the index finger (B). To keep the coffee from spilling, the rotational force at (B) must be countered by an equal and opposite force- the knuckle of the middle finger (C). This, pressed against the cup heats up from the temperature passing through the wall of the cup (D) causing a cry of pain from the drinker (OW).
It reminded me of the most concise example of the phrase "Form Follows Function" that I discovered in Architecture school. Below is an excerpt of that text.
From Lectures on Architecture, Eugène Emmanuel Violet-le-Duc. Vol 1., Dover Publications, New York,, 1987