Measurement – Physics Form 1. measurement is **the process of associating numbers with physical quantities and phenomena**. Measurement is fundamental to the sciences; to engineering, construction, and other technical fields; and to almost all everyday activities

Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared to a basic reference quantity of the same kind

## Basic Fundamental Quantities

A Fundamental Quantity

A quantity is the amount, size or extent of a material, object or event expressed in numbers. Examples of quantities are mass, speed, distance, force, and energy. A quantity has two parts, a number and a unit e.g. A mass of 12 kg has ‘12’ as a number and ‘kg’ as a unit.

**A Unit **is the standard which is used to explain measurement of a body like; kilogram, metre, seconds etc.

A quantity may be fundamental or derived. A fundamental quantity is the quantity which cannot be explained in form of other quantities. There are seven fundamental physical quantities namely mass, length, time, temperature, electric current, amount of substance and luminous intensity. Fundamental quantities cannot be derived into other quantities.

## Three Basic Fundamental Quantities of Measurement

Mention three basic fundamental quantities of measurement

Among the seven fundamental physical quantities, there are three basic fundamental quantities which are mass, length and time.

Mass is defined as the amount of matter contained in a body. Length is the distance between two points or objects, while, time can be defined as the gap or space between events. Measurement – Physics Form 1

## The S.I Unit of Fundamental Quantity

**SI unit **(International system of units): Is the system of units which is used internationally to measure seven basic physical quantities.

SI units of fundamental quantities

Fundamental quantity | SI unit | Unit symbol | Other common units |

Mass | Kilogram | kg | Tones (t), gram (g) |

Length | Metre | m | Kilometre (km), centimetre (cm), millimetre (mm) |

Time | Second | s | Hours (hr), minutes (min) |

Temperature | Kelvin | K | Centigrade degrees (), Fahrenheit degrees () |

Luminous intensity | Candela | cd | Candle power |

Amount of substance | Mole | mol | Pound mole (lb-mol) |

Electric current | Ampere | A | No other units |

**Note**: With the exception of temperature, amount of substance and luminous intensity, other units of measurement that are smaller or larger than the most commonly used units are expressed by attaching a prefix to the most commonly used units.

Greater than 1 unit

- Giga(G) = 1,000,000,000 (10ˆ9)
- Mega(M) = 1,000,000 (10ˆ6)
- Kilo(K) = 1,000(10ˆ3)
- Hector (h) = 100(10ˆ2)
- Decca(da) = 10(10ˆ1)1

Less than 1 unit

- Deci (d) = 1/10 (10ˆ-1)
- Cent (c) = 1/100(10ˆ-2)
- Mill (m) = 1/1000 (10ˆ-3)
- Micro(μ) = 1/1,000,000(10ˆ-6)

## Appropriate Instruments for Measuring Fundamental Quantities

Measurement of length

Length is the distance between two points, objects or space. The SI unit of length is **meter **(m). Other commonly used units are **kilometer **(km) and **centimeter **(cm). In the laboratory, length is measured by using instruments such as meter rule, vernier caliper and micrometer screw gauge.

**Meter rule**

It measures length to the accuracy of 0.001 m or 0.1 cm. It is calibrated from 1 cm to 100 cm which is equal to 1m length. It is used to measure linear length (lengths with no curves).

How it works

- Align a meter rule close and along the edge of the length of the object to be measured.
- Take the reading by looking at the mark from vertically upwards to avoid parallax errors.
- Record the reading.

**Vernier caliper**

It measures length to the accuracy of **0.01cm (0.1mm). **It is used to measure lengths to the range of 1.0cm to about 12.0cm. It has two scales namely main scale and vernier scale. The main scale is marked in cm from 1 cm to 12 cm while the vernier scale is marked with 10 marks measured in mm. It has two outside jaws used to measure length and external diameter of cylinders and pipes. It has two internal jaws for measuring internal diameter of cylinders and pipes. Measurement – Physics Form 1

The inside jaws are used to measure the inside diameter while the outside jaws are used to measure outside diameter. The vernier slides over the main scale.

**How to read:**

- Fit the object to be measured between the jaws, make sure not to press the object.
- Record the reading on the main scale by reading the mark which is just behind the zero mark of the vernier scale.
- Record the reading on the vernier scale by reading the mark which coincides with the mark on the main scale.
- The length of the object is obtained by adding the reading from the main scale and the reading on the vernier scale.

**Micrometer screw gauge**

It measures small lengths to the accuracy of **0.001cm (0.01mm). **It is used to measure the diameter of wires and ball bearings. It can measure small lengths up to about 2.5cm. It has a spindle with a linear scale on one of its side. It has a vernier scale (circular scale) on its thimble. The vernier scale has 50 equal marks each measuring 0.5mm.

**How to read a micrometer screw gauge:**

- After fitting the object between the anvil and spindle, take the reading on the linear scale by recording the last mark visible. The reading is in mm.
- Record the reading if there is a mark below the datum line or reference line.
- Take the reading on the vernier scale by recording the mark which coincides with the datum line of the sleeve in mm.
- The length/diameter of the object in mm is obtained by adding the two readings.

**Precautions when using a micrometer screw gauge:**

- Before use, the faces of anvil and spindle should be wiped clean to remove any dirty particle which would give false readings.
- Check and record for zero error then + or –the correction to the final answer. Measurement – Physics Form 1

**Time**

It is the gap between two occasions or events. The SI unit of time is **second **(s). Other units used are minutes (min), hours (h), days, etc.

1min = 60s

1h = 3600s

1day = 86400s

The instruments for measuring time are **clocks** and **watches**.

In the laboratory, time is measured by using the stopwatch. Stop watches are used for timing laboratory experiments. Stop watches may be mechanical or digital. Digital stop watches are more accurate than mechanical stop watches.