Berat

Untuk kegunaan lain, lihat Berat (disambiguasi).

Dalam fisika, berat dari suatu benda adalah gaya yang disebabkan oleh gravitasi berkaitan dengan massa benda tersebut. Massa benda adalah tetap di mana-mana, namun berat sebuah benda akan berubah-ubah sesuai dengan besarnya percepatan gravitasi di tempat tersebut.

A neraca pegas untuk mengukur berat suatu obyek.

Berat dihitung dengan mengalikan massa sebuah benda dengan percepatan gravitasi di mana benda tersebut berada. Berat sebuah benda di bumi akan berbeda dengan beratnya di bulan. Sebuah benda bermassa 10 kilogram, akan tetap mempunyai massa 10 kilogram di bumi maupun di bulan, namun di bumi benda tersebut akan mempunyai berat 98 Newton, sedangkan di bulan, benda tersebut akan mempunyai berat 16,3 Newton saja.

Rumus untuk berat:

$\!W=m.g$

Dengan $\!g$ percepatan gravitasi, $\!m$ massa benda dan $\!W$ berat benda. Satuan SI (Sistem International) untuk berat adalah newton (N).

Berat dan massa

In modern usage, weight and mass are fundamentally different quantities: mass is an intrinsic property of matter, whereas weight is a force that results from the action of gravity on matter.

However, the recognition of this difference is, historically, a relatively recent development – and in many everyday situations the word "weight" continues to be used when "mass" is meant. For example, we say that an object "weighs one kilogram", even though the kilogram is a unit of mass.

The distinction between mass and weight is unimportant for many practical purposes because, to a reasonable approximation, the strength of gravity is the same everywhere on the surface of the Earth. In such a constant gravitational field, the gravitational force exerted on an object (its weight) is directly proportional to its mass. So, if object A weighs, say, 10 times as much as object B, then object A's mass is 10 times that of object B. This means that an object's mass can be measured indirectly by its weight (for conversion formulas see below). For example, when we buy a bag of sugar we can measure its weight (how hard it presses down on the scales) and be sure that this will give a good indication of the quantity that we are actually interested in, which is the mass of sugar in the bag. Nevertheless, slight variations in the Earth's gravitational field do exist (see Earth's gravity). These alter the relationship between weight and mass, and must be taken into account in high precision weight measurements that are intended to indirectly measure mass.