The “scientific study” chapter covers the following topics:

- 1.0. Introduction
- 1.1. Variables of Scientific Research
- 1.2. Types of Units

Besides these, we will cover some unit-wise analysis of equations formulae. Find the class 10 science and technology book pdf. This book is a new edition (2080) syllabus based on CDC Nepal.

**Question Marking** – 1 Very Short Question (1Mark) + 1 Short Question (2Marks) = 3Marks

## Introduction

**Scientific Study** is the study of any event involving the scientific process, models, theory, or experiment.

**Scientific Variables** are the measurable quantities and conditions that are used to alter the test and can be controlled or changed during the scientific experiment. Variables are those parameters that measure, alter or change the experiments.

## Variables of Scientific Research

There are usually 3 types of variables in scientific research. Before learning about the types of scientific variables, let’s discuss an activity.

**Activity 1.1**

Title: Rubber Band Catapult Experiment

**Materials Needed:**

- Rubber Band Catapult
- 15 Cm Ruler
- Small pieces of paper
- Measuring Tape

**Procedure:**

- Set up the rubber band catapult by holding the catapult end (handle) with a hand and holding the catapult arm using another arm.
- Place the small piece of paper on the catapult arm.
- Stretch the arm by measuring the distance between the catapult end and the catapult arm. Start with a 4 cm stretch.
- Release the catapult arm, the paper flies away. Note how much distance the paper flies away from the catapult using a measuring tape.
- Repeat the procedure for stretch lengths 6, 8, and 10 cm and also measure the corresponding distance the paper covers.

S.N | stretched length of rubber band (cm) | Distance Covered by the Paper (m) |

1. | 4 | |

2. | 6 | |

3. | 8 | |

4. | 10 |

While performing any scientific research or experiments, only one of the physical quantities is made variable (changed), and change in another quantity is measured with respect to that physical quantity. For example, in the **activity1.1** stretch length of the catapult band is varied time and again, and a change in distance covered by the paper is observed. Here both the stretch length and distance covered by the paper are physical quantities but their values are different in each experiment. These types of quantities are known as **Variables**. In other words, variables are those physical quantities whose values can be changed in scientific experiments.

## Types of Variables

Variables of scientific research are classified into three types.

**Independent Variables**– Independent Variables are those variables whose values do not depend upon other variables but only depend upon the person doing the experiment. In**Activity 1.1**, the stretch length does not depend upon any other variables, so it is an example of the independent variable.**Dependent Variable**– Now observe the distance covered by the paper. It depends upon the stretch of the rubber band. So, it is a dependent variable. Thus Dependent Variable is the variable that depends upon other independent variables.**Controlled Variable**– For better accuracy of the experiment, all the other variables besides the dependent and independent variables are kept constant (unchanged) which is also known as the controlled variable. In the above experiment, the length of the catapult rubber band and the size of the paper are kept the same in each experiment which are examples of controlled variables.

Referring to Activity 1.1Independent Variable – Stretch Length of Catapult BandDependent Variable – Distance Covered by the PaperControlled Variable – Length of Catapult Rubber Band, Size of paper pieces |

## Types of Units

Physical quantities are measured with reference known standard quantities known as units, Units are classified into two types.

**Fundamental Units**– Fundamental units are those units that do not depend upon any other units. For example, Kg is the fundamental unit of mass which does not depend upon any other units. In the SI system of units, there are 7 fundamental units.

S.N. | Physical Quantity | Unit | Symbol |

1. | length | meter | m |

2. | mass | kilogram | kg |

3. | time | second | s |

4. | temperature | kelvin | K |

5. | luminous intensity | candela | cd |

6. | amount of substance | mole | mol |

7. | electric current | ampere | A |

2. **Derived Units** – Derived units are those units that are derived from the fundamental units and depend upon the fundamental units. For example, the Unit of velocity is m/s. which depends upon two fundamental units meter(m) and second(s).

Some of the derived units that are used in daily practice are:

S.N. | Physical Quantity | Derived Unit | Involved Fundamental Units |

1. | Area | m^{2} | m |

2. | Velocity | m/s | m, s |

3. | Density | kg/m^{3} | kg, m |

4. | Force | kg*m/s^{2} | kg, m, s |

5. | Acceleration | m/s^{2} | m, s |

**Q.** Why is Newton a derived unit?

**Ans**. Newton is a unit of force. Force=mass*acceleration

N=kg*m/s^{2}. Newton is derived from other fundamental units kg, m, and s. Thus Newton is a fundamental unit. Here kg is the fundamental unit of mass and acceleration is a derived unit of m and s.

## Analysis of unit-wise equation

Different equations and formulas are obtained from scientific experiments and research. The homogeneity of equations and physical quantities in an equation can be checked by analysis of units. For equations to be valid, homogeneous equity must occur between the fundamental units of both sides. For example, In unit-wise equation analysis of equation s=v*t, the fundamental unit of the left-hand side is ‘m’ and the right-hand side is m*s/s =m which is the same. Thus this equation is a valid equation.

If someone claims s=v/t, the by-unit analysis, the fundamental unit of the lefthand side is meter (m) and the righthand side is m/s*s=m/s^{2}, which is not equal to the fundamental unit of the lefthand side which is m. Then, we can identify that equation is wrong using the help of an analysis of units. Also, only physical quantities with the same units can be added to or subtracted from each other.

### Importance of unit-wise equation analysis

Unit-wise equation analysis is needed to test the accuracy of the physical equations, identify the relations between two physical quantities, and convert units into different systems of measurement.

## Conclusion

After reading this students will be able to

- Know the basics of scientific study
- Define and classify the variables
- Differentiate between fundamental and derived units
- Unit-wise equations of different equations.

By reading this, chapter you will get fundamental knowledge about scientific study, variables, and units. You will be able to test the accuracy of the various physical equations. Find important questions and solved exercise of Chapter 1 from here.