Mass is the quantity of matter contained in an object. It depends on what type of atoms the object is made from and how many atoms there are.
The most common way to measure the mass of an object is by weighing it. This can be done on scales or by using simple balancing techniques.
The metric system
The metric system is an international decimal measurement system that uses the metre, kilogram and second as base units. These units represent fundamental orthogonal dimensions of the physical world.
The system was first adopted in France in 1791 and has become the most commonly used standard in the world. It was developed in order to replace the complex system of slugs, pounds and tons that had been used since ancient times.
Metric bases were chosen for their relationship to the basic units in each of the other four dimensions of measurement: length (distance), capacity, weight and time. They also represented the logical relationships that are inherent in the physical system.
The metric system is based on the powers of ten, so it makes conversions easy. The metric prefixes are six common ones, and they represent the powers of ten, so these are used to convert from one metric unit to another.
Digital and spring scales
Scales are an essential tool in mass measurement because they provide a precise reading of an object’s weight or mass. They are used in many different industries, including manufacturing, transportation and retail.
A digital scale uses computerized technology to measure and display weight. Its measurements are displayed as numbers, usually on a liquid crystal display (LCD).
Spring scales use Hooke’s law to determine the weight of an object by measuring the force required for stretching or compressing a spring. The units of measurement on a spring scale are Newtons.
The accuracy of a scale depends on the materials used in its construction and how it is used. Over time, a scale can lose its sensitivity and require periodic adjustment to keep it working properly. This is called calibration and takes place at the location of use.
Slam loads are those arising when an object penetrates the water surface with significant velocity. They can be very sensitive to precise local conditions at the time of impact, and may be difficult to model accurately.
SLAMMED is an approach to modelling slamming. It uses constant slam coefficients for both water entry and exit to represent the effects of a surface-piercing object.
For a horizontal cylinder, these are defined in terms of
In addition, a user-specified variable slam data value is given as the rate of change of added mass with normalised submergence. This value is usually positive for water entry, and negative for water exit.
The constant slam coefficients and user-specified variable slam values are truncated at both ends of the range to ensure that the force is always zero when the object is out of the water, and reduces to zero once it is below the surface. This also ensures that the force is consistent in both directions, if the object pierces the surface in one direction and then leaves the water in another.
The beam balance
The beam balance is a simple device for measuring mass. It consists of two ‘pans’ suspended by chains and a beam connected to them.
The pans are designed to accommodate a wide range of substances and weights. The beam has a light pointer that moves over a scale and indicates when the masses of an object match.
A beam balance also allows the user to read the mass in grams rather than units of force (newton). However, since weight depends on gravity and a balance requires some amount of it to work, this means that the results will be erroneous when used on Mars or the moon.
The triple beam balance is a popular instrument for mass measurement in chemistry and physics laboratories. It is very sensitive and accurate, having a reading error of +-0.05 grams.