Kitchen Scales

A weighing scale (usually just "scale" in common usage; except in Australian English where "scales" is more common) is a device for measuring the weight of an object (the gravitational attraction between the object and the Earth). more...

Most are Spring Scales and others are just balances (that measure mass) that are calibrated to display weight, since an object's weight is directly proportional to its mass (how much material the object contains). Weighing scales are often used to measure the weight of a person, and in many industrial and commercial applications, scales are used to determine the weight of things ranging from feathers to loaded tractor-trailers.

Balance

A balance (also balance scale, beam balance or laboratory balance) is used to measure the weight of an object. In its conventional form, this class of measuring instrument compares the weight of a sample, placed in a weighing pan, also called scale (hence the term "scales") scalepan, or bason (obsolete ) and suspended from one end of a beam with standard weights in another pan suspended from the other end. To determine the weight of an object in the measuring pan, standard weights are added to the balance pan until the beam is in equilibrium as closely as possible. Then a slider weight (not always present) is moved along a second beam that is on or parallel to the main beam (and attached to it) until fine balance is achieved. The slider position gives a fine correction to the weight value. Since the mass of an object is proportional to its weight, a balance can be labeled to display the object's mass.

A change in the strength of the locally uniform gravitational field (taking the balance to the top of a mountain, or to the Moon...) will not change the measured mass. The moments of force on either side of the balance are affected equally by any change in gravitational field.

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