##### Chapter 1

## Physical Quantities and Measurement

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

#### Introduction

Length is a measurement used to calculate the distance between two objects or two points within an object. For example, the distance between the ends of a tennis court or the height of your body. Distances are measured in centimetres, metres, kilometres, miles, inches, feet etc. SI unit of length is in metres.

**Measurement of length** is done using scales for straight lines, threads for curved lines, callipers for diameters. The multiples of length and their submultiples are mentioned below:

- 1metre (m) = 10 decametres (dam)
- 1 m = 100 centimetres (cm)
- 1000 m = 1 kilometre (km)

Time is a physical quantity to measure the passage of duration. The difference between the start and end of an event is known as duration. For example, the difference between the afternoon and midnight is 12 hours. This duration is calculated as time.

**Measurement of time** is done using watches and clocks. Earlier, the sun’s direction, phases of the moon, light and shadow were used to measure the passage of time. The SI unit of time is in seconds(s). Few multiples of time are mentioned below:

- 1 year = 365 days
- 1 year = 12 months
- 1 week = 7 days
- 1 day = 24 hours
- 1 hour = 60 minutes
- 1 minute = 60 seconds

The mass of an object is the amount of matter present in a body. The SI unit of mass is a kilogram. Few other units of mass are gram, pound, ounce, and milligram. The **measurement of mass** is traditionally performed using scales and balances. A beam scale compares the mass of the object with a standard mass, whereas a spring scale measures the object’s distance. When an object is under the influence of gravity, it is called weight. Hence, we usually measure the weight of the objects. The conversions of units of mass are as follows:

- 1000 gram (g) = 1 Kilogram (kg)
- 1 g = 100 milligrams (mg)
- 1 pound = 453.59 g

The temperature of an object is measured as the degree of hotness or coldness of its body. For example, Boiling water is hot (100 celsius), whereas an ice cube is cold (0 celsius). This difference in the perception of the temperature of an object is measurable. The SI unit of temperature is Kelvin (K), although Celsius (C) and Fahrenheit (F) are the most commonly used **measurement of temperature**.

The temperature of an object is calculated using a thermometer. The human body is measured using clinical mercury or digital thermometer. The temperature of a living human body is 37 degrees Celsius or 98.6 degrees Fahrenheit. Various units of **measurement of temperature** are mentioned below:

- 273 kelvin = 0 degrees Celsius
- 273 Kelvin = 37.3 degrees Fahrenheit

The measurement of land, two-dimensional or three-dimensional objects is done using the physical quantity called area. The SI unit of area is square meters. An area is calculated by multiplying the length of either side of the object. For example:

- Length x breadth of a rectangle = area of a rectangle.
- Length x length of square = area of the square
- ½ x base of triangle x height of triangle = area of the triangle
- Π x radius x radius = area of a circle

Graph papers are used to calculate the area of these shapes on a piece of paper. The number of squares covered in the graph sheet is the area of the object. Suppose, you have to measure the area of a fallen leaf. Then you have to draw the outline of the leaf on graph paper, the total number of squares becomes the area of the leaf. The **measurement of area** of land is done using hectares, yards, acres, square kilometres. Below mentioned are a few multiples of area units :

1 square kilometres (km)= 1000 m x 1000m

1 hectare = 100m x 100m

1 square kilometres = 100 hectares