# The Importance of Mass Measurement

When measuring mass in a laboratory, students often use a balance or scale. Before using the balance, it is important to tare it and make sure it is clean. It is also important to ensure the environment is free of air movement as this will impact the accuracy of the measurements.

## Weight

It is important for kids to understand the difference between mass and weight, especially as they get ready to tackle the metric system in chemistry and biology classes. It will help them grasp the more complicated concepts in physics and mathematics later on.

Measuring mass is most often done with a balance (not a scale). This instrument measures the force that an object’s matter exerts on another object by using a set of known masses to calibrate it. This type of measurement requires some level of gravity, so it would not work on the moon or in space.

The amount of matter in an object’s matter is its mass, but the force that gravity exerts on an object’s matter is its weight. Your 88-pound weight on Earth will be different from your 40-kilogram weight on the moon, and even less than that on Jupiter. Because gravity is weaker on other planets, weight decreases. This is why we use kilograms to measure mass, while pounds are used for the more familiar bathroom scale.

## Gravity

Gravity is the force that causes all matter to attract everything else, from subatomic particles to clusters of galaxies. It’s a universal force, operating across any distance, although it weakens as the distance between the objects increases.

Although it’s commonly used as a synonym for mass, weight is actually a measure of the gravitational pull, not of an object’s amount of matter. This distinction is important because your weight can change depending on where you are – it’s stronger on Earth than on the Moon, for example.

Gravity has also helped uncover some monumental discoveries, such as finding that stars at the edges of galaxies orbit faster than they should if only light were responsible for their motion. More recently, scientists have started to detect ripples in spacetime called gravitational waves when massive objects like neutron stars and black holes collide. These signals have opened up a whole new window into the universe. The challenge now is to bring together gravity with quantum mechanics in a theory of everything.

## Force

Mass measurement impacts our daily lives, whether we purchase groceries or design a bridge, space shuttle or automobile. To ensure that products and processes are accurate, fair, and safe, uniform standards must be maintained to support trade and commerce. Mass measurements play a vital role in this global endeavor.

Precise mass measurements require the ability to compare two masses under controlled conditions. This includes eliminating the effects of friction and gravity. To do this, one must apply a known force to the standard mass, ms, and measure its acceleration. Then, using a balance with the same calibration, one must apply that same force to another unknown mass, mu, and measure its acceleration. The difference in these accelerations is the net (unbalanced) force. This is measured in newtons, a unit defined as the force required to accelerate a kilogram of mass by one meter per second squared. Statistical process control procedures are applied to mass measurements and the results, known as accepted values, are plotted on control charts.

## Acceleration

The acceleration of an object tells you the rate at which its velocity changes over time. It is a vector quantity, as it has both magnitude and direction, unlike mass which is a scalar quantity.

Acceleration is measured in meters per second squared (m s 2). The units may seem a bit awkward at first, but they make sense once you see the acceleration equation.

The direction of the acceleration is determined by adding together all the forces that act on the body, and this must be done vectorially – each force has a head and a tail. The direction of the tail of the vector is equal to the acceleration, so it points in the same direction. This makes it easier to understand why passengers lean back when the bus accelerates. They are reacting to the fact that their inertia is pointing backwards against the acceleration. This is the same reason that two masses can be compared by balancing them on a balance.

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