The metric system is based on multiples of 10. That means that a meter is 100 times larger than a centimeter, and a kilogram is 1,000 times heavier than a gram. This makes the system much easier to understand than a U.S. customary system of 3 feet equaling 1 yard.
Active gravitational mass
The force that an object exerts on itself and on other objects is proportional to its mass, as defined by Newton’s second law of motion. This is what makes the objects feel the same acceleration, or weight, when they are dropped from the same height. Physicists have determined that there are two conceptually distinct types of mass: inertial and passive gravitational mass.
The inertial type of mass determines the resistance an object has to acceleration (a change in its state of motion). This can be measured with a balance, as shown in this Papyrus of Hunefer illustration from the 19th Dynasty, c. 1285 BCE.
In a similar experiment, Galileo demonstrated that freely falling bodies reach the ground together irrespective of their internal composition. This is one of the most famous test results in physics and was used by Einstein as the basis for his equivalence principle. It is based on the assumption that an object’s active gravitational mass is equal to its free-fall acceleration times its inertial mass, or F = M
Passive gravitational mass
The concept of mass is an important one in physics. It determines how much an object resists the application of force and allows for calculations of its velocity, momentum, and Newton’s three laws of motion. There are three different types of masses: inertial, active gravitational, and passive gravitational. While they appear to be independent of each other, they are actually related by their gravitational fields. Physicists have performed many experiments to try to find differences between inertial and passive gravitational mass, but none of them have been successful.
The weak equivalence principle states that the force of gravity and inertial mass are proportional to each other. This means that the same acceleration will be experienced by objects with the same inertial mass, regardless of the material composition of the objects. This is verified experimentally by dropping different objects and observing their free fall. This is done using an apex-style balance, which is a type of spring scale.
Weight
Many people use the terms “mass” and “weight” interchangeably, but they are distinctly different. Mass measures the total matter contained in an object, while weight is the force exerted by an object due to gravity.
Gravity is a universal constant, and the same amount of matter will have the same gravitational pull no matter where it is on the Earth. However, the force of gravity varies from place to place, so an object with the same mass will have a different weight at a different location.
Weight is measured in units called newtons (N), which are equal to the force required to accelerate a kilogram of mass at a rate of one kilogram per second squared. Other weight units have also been used, such as the pound-force (lbf) and the dyne (used in the CGS system). These are not part of the SI system.
Mass-measuring instruments
In scientific and practical applications, it is crucial to have mass-measuring instruments that are accurate and reliable. This can help ensure that products are consistent and safe, and that experiments are performed correctly. These instruments can come in a variety of forms and are used in different contexts. They can range from simple balances to more advanced weighing machines.
The most common instruments for measuring mass are weighing scales. These work on the principle that an unknown object’s weight is proportional to the force of gravity acting on it. They can come in a variety of designs, from mechanical spring scales to digital electronic scales.
The Army needs to make precise mass measurements for a wide range of purposes, from determining medication dosages to ensuring that equipment is light enough to fly on an airplane. Currently, the Army sends its mass standards to NIST, which uses its Kibble balance to perform calibrations that are directly traceable to the International System of Units (SI). The Army is also working with NIST to develop a tabletop version of the Kibble balance.