NCERT Solutions for Class 11 Physics, Chapter 2 - Units and Measurement

In this chapter, you will learn about units and base units as well as how to make measurements. Every physical body that is measured is based upon a number to finalise its quantity. Chapter 2 of the book, Physics Part-I, has 10 sub-sections with each section detailing into the various aspects of the chapter. In this chapter, you will learn about the international system of units, how to measure length, mass and time. The NCERT Solutions for Class 11 Physics Chapter 2 Pdf Download will further aid you in your study.

Let us take a look at the subtopics of Class 11 Physics, Chapter 2, Units and Measurement.

2.1 Introduction

2.2 The international system of units

2.3 Measurement of length

2.4 Measurement of mass

2.5 Measurement of time

2.6 Accuracy, precision of instruments and errors in measurement

2.7 Significant figures

2.8 Dimensions of physical quantities

2.9 Dimensional formulae and dimensional equations

2.10 Dimensional analysis and its applications

In class 11 Physics. Chapter 2, you will learn:

Section 2.1 – In this section, you will study the comparison and the need for the internationally set standards known as units, which are used in order to measure physical quantities. For example, some of the units include kg (kilogram), cm (centimetre), etc.

Section 2.2 – This section will tell you about the various different systems of measurements that scientists have come up with, over time. The basic units for the measurement of length, mass and time are as follows:

CGS system – centimetre, gram and second.

FPS system – foot, pound and second.

MKS system – metre, kilogram and second.

Section 2.3 – Do you know that length can be measured in a lot of different ways? It depends on the actual size of the object that is to be measured. In this section, you’ll learn that in order to measure long distances, such as the distance between the Earth and the Sun, the parallax method is used. However, for measuring the length of molecules or atoms, other methods have to be used.

Section 2.4 – In this section, you will learn about the SI unit of mass is kilogram. However, for measuring the mass of objects ranging from atoms to the Sun, a kilogram cannot be used all the time. Other units of mass are then used accordingly.

Section 2.5 -You already know that to measure any time interval, a clock is needed. In this section, you will learn that we now use an atomic standard of time, which is based on the periodic vibrations produced in a caesium atom. This is the basis of the caesium clock, sometimes called atomic clock, used in the national standards. In order to understand this portion better refer to Units and Measurements Class 11 Numericals with Solutions here at UrbanPro.

Section 2.6 – This section will tell you why measurement is a very important aspect of science and technology. You will also come to know that there is always uncertainty when it comes to taking the exact measurement. This uncertainty is known as error.

Errors can be of two types:

1. Systematic error:

1. Instrumental error

2. Imperfection in the procedure

3. Personal error

2. Random error – Errors that take place randomly concerning their size and signs. These errors are unpredictable.

3. Least count error – this arises while measuring the value of the smallest measurement offered by an instrument.

Section 2.7 – Errors in measurement are something that can’t be totally eradicated. In this section, you’ll learn that measurement should be reported in a way that indicates its precision. It should be a number that includes all digits in the number that are known reliably plus the first uncertain digit. Together, the reliable and uncertain digits are known as significant numbers. For more information, you can refer NCERT Solutions for Class 11 Physics Chapter 2 here at UrbanPro.

Section 2.8 – In this section, you will study that physical quantities are described by their dimensions. The powers to which the base quantities are raised, to represent the quantity, are known as the dimension of that physical quantity.

Section 2.9 – This section deals with the equation that is derived by equating a physical quantity with its dimensional formula. It is called the dimensional equation of the physical quantity.

Section 2.10 – At the end of this chapter, you will understand the need to have a  good grasp over the topic of dimensional analysis; and how it helps in understanding the relations among different physical quantities and checking the derivation, accuracy and dimensional consistency or homogeneity of various mathematical expressions.