If that physical property is weight, you can use what is known as a load cell. [DegrawSt] uses four 50 kg load cells to create a bathroom scale using an Arduino.

In this video we electroplate SLA samples with Acid Copper and Bright Nickel, then test their tensile and ultimate strength ...

Using the ever-popular Arduino Uno, the feeder is connected to a platform that uses load cells to detect the pet’s weight. The weight data is then used to identify which animal is looking for food.