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# MEASUREMENT IN PHYSICS

## MEASUREMENT IN PHYSICS

1. Measurement of length
2. Measurement of mass & weight

## MEASUREMENT OF LENGTH/DISTANCE

Length is measured using the following instruments.

(a). Metre Rule: A metre rule is a measuring device calibrated in centimetres (cm) with a range of 0 – 100cm. In using the metre rule, the eye must be fixed vertically on the calibration to avoid parallax errors.The smallest reading that can be obtained on a metre rule is 0.1cm (0.01cm).

(b). Callipers:these are used in conjunction with metre rule for measuring diameter of tubes, thickness of sheet, etc. The callipers are of two types –

• The external calliper and
• The internal calliper.

The external calliper is used to measure the external diameters of solid objects; while the internal calliper is used to measure the internal diameters of solid objects.

(c) Vernier calliper

The vernier calliper can be used for measuring smalllinear length and diameters of objects within the  range of 0-12cm at least. It is calibrated in centimetres (cm). It has a reading accuracy of 0.1mm (0.01cm)

(c). The micrometer screw gauge: It is used to measure the thickness of a round objects  E.g, the diameter of a wire.  The micrometer screw guage gives a more accurate reading than the vernier calliper. It is calibrated in millimetre (mm). It has a reading accuracy of 0.01mm (0.001cm)

Other instruments for measuring length include: measuring tape, ruler, etc. The S.I. unit of length is metre (m).

Evaluation:

1. Mention any three instrument used in measuring length.
2. Which of the above instrument could give the highest degree of accuracy?

## MEASUREMENT OF MASS/WEIGHT

Mass is defined as the quantity of matter a body contains; while Weight is the amount of gravitational force acting on a body or the force with which a body is attracted towards the centre of the earth. The weight of a substance varies from place to place due to variation in acceleration due to gravity,‘g’ over places but mass remains constant from place to place.

Mass and weight of objects are measured using instrument such as spring balance, beam balance, chemical balance, scale balance, etc.

However, the difference between mass and weight is shown below.

 S/N MASS WEIGHT 1. Mass is a scalar quantity. Weight is a vector quantity. 2. Mass is the amount of stuff or quantity of matter contained in a body. Weight is the amount of gravitational force acting on a body. 3. Mass is measured using a beam balance, chemical balance Weight is measured using spring balance. 4. The S.I. unit of mass is kilogramme (kg) The S.I. unit of weight is Newton (N).