In science, measurement refers to all efforts taken to quantify physical quantities. Physical quantities include mass, weight, temperature and many others. Measurement aims at getting the exact or close numerical magnitude of physical or scientific quantities.
Instruments that are used to measure quantities are called Measuring Instruments.
For example, length is measured with the use of a metre rule and temperature of an object is measured with the use of a thermometer.
Every instrument has their own accuracy, which is their spectacular ability to detect values close to the exact magnitude of the quantities they measure.
The accuracy of a:
- Metre rule is 0.1cm or 1mm.
- Vernier caliper, which is used for measuring small lengths, is 0.01cm.
- Micrometer Screw Gauge is 0.01mm.
Physical quantities can be divided into two categories, depending on their possession of magnitude and direction or magnitude only. The categories are:
- Scalar quantities.
- Vector quantities.
Scalar quantities are quantities that have only magnitude but no direction. They have values but no specific direction in which they act. Examples of such quantities are Temperature, Area, Volume, Length, Electric Potential, Magnetic Flux to mention but a few.
Vector quantities, on the other hand, are quantities that have both magnitude and direction. They have specific numerical values and they have directions that their qualities are channeled towards. Examples of vector quantities include Weight, Upthrust, Momentum of a body, Moment of a force, Velocity of a moving body; the list goes on and on.
Scalar quantities can be added numerically, as in simple addition, with no complex method. This is because they have no direction. For instance, combination of water of volume 3cm³ and another sample of water of volume 5cm³ will resultantly give 8cm³.
Vector quantities, however, are combined in both their magnitudes and directions. In fact, a vector quantity with given magnitude but no direction has incomplete information about it. Both magnitude and direction give full details about the quantity. If the velocity of a body is given as 20m/s only, more information is still needed. The direction must be given. It would be completed if it were written as 20m/s at N 60° W.
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