Namaste! As your Science teacher, I am here to help you master **Unit 7: Force and
Motion** based on your notes and the Nepal curriculum. This unit is very important for
your **SEE (Secondary Education Examination)**. Let’s break down the key concepts
you need to succeed.
### 1. Newton’s Universal Law of Gravitation
The first thing you must understand is that **gravitation** is the force of attraction
between any two objects in the universe [1].
**The Law states:**
* The gravitational force ($F$) is **directly proportional** to the product of the masses
($m_1$ and $m_2$) of the two objects [2].
* The force is **inversely proportional** to the square of the distance ($d^2$) between
their centers [2].
**Mathematical Derivation:**
By combining these two points, we get the formula:
$$F = G \frac{m_1 m_2}{d^2}$$ [1, 2].
**Universal Gravitational Constant (G):**
* **Definition:** It is the force between two objects of $1\text{ kg}$ mass each,
separated by a distance of $1\text{ m}$ [3].
* **Value:** $6.67 \times 10^{-11} \text{ Nm}^2/\text{kg}^2$ [3].
* **Exam Tip:** Remember this value and its unit for numerical problems! [4].
### 2. Gravity and Acceleration due to Gravity ($g$)
While gravitation is between any two objects, **Gravity** is the specific pulling force
exerted by a planet or satellite towards its center [5].
**Acceleration due to gravity ($g$):**
This is the acceleration produced in a freely falling object due to gravity [5]. Its average
value on Earth is $9.8 \text{ m/s}^2$ [5].
Motion** based on your notes and the Nepal curriculum. This unit is very important for
your **SEE (Secondary Education Examination)**. Let’s break down the key concepts
you need to succeed.
### 1. Newton’s Universal Law of Gravitation
The first thing you must understand is that **gravitation** is the force of attraction
between any two objects in the universe [1].
**The Law states:**
* The gravitational force ($F$) is **directly proportional** to the product of the masses
($m_1$ and $m_2$) of the two objects [2].
* The force is **inversely proportional** to the square of the distance ($d^2$) between
their centers [2].
**Mathematical Derivation:**
By combining these two points, we get the formula:
$$F = G \frac{m_1 m_2}{d^2}$$ [1, 2].
**Universal Gravitational Constant (G):**
* **Definition:** It is the force between two objects of $1\text{ kg}$ mass each,
separated by a distance of $1\text{ m}$ [3].
* **Value:** $6.67 \times 10^{-11} \text{ Nm}^2/\text{kg}^2$ [3].
* **Exam Tip:** Remember this value and its unit for numerical problems! [4].
### 2. Gravity and Acceleration due to Gravity ($g$)
While gravitation is between any two objects, **Gravity** is the specific pulling force
exerted by a planet or satellite towards its center [5].
**Acceleration due to gravity ($g$):**
This is the acceleration produced in a freely falling object due to gravity [5]. Its average
value on Earth is $9.8 \text{ m/s}^2$ [5].
