33106 Chapter Notes - Chapter 1: Caesium, Cross Product, Kilogram
Document Summary
Range of validity: theories have a range of validity - they apply under certain conditions. Physical quantity: a number used to describe a physical phenomenon. Operational de nition: certain quantities that are so fundamental they are de ned by how they are measured. Unit: a standard quantity, such as 1 meter or 1 second. International system (si): an o cial metric system that de nes fundamental units. Second: de ned as the time required for 9,192,631,770 cycles of the energy state of a cesium atom under microwaves of a particular frequency. Meter: de ned as the distance light travels in a vacuum in 1/299, 792, 458 seconds. Kilogram: de ned as the mass of a particular cylinder of platinum-iridium alloy kept at the international bureau of. Dimensionally consistent: equations must be consistent in the units on both sides of any mathematical operation.
