📌 Key Topics:
- Balanced and Unbalanced Forces
- First Law of Motion
- Inertia and Mass
- Second Law of Motion
- Third Law of Motion
- Conservation of Momentum
🔹 1. Balanced and Unbalanced Forces
- Force is a push or pull on an object.
- Balanced Forces: When forces acting on a body from opposite directions are equal in magnitude, the object does not move.
🟢 Example: Tug of war with equal force on both sides. - Unbalanced Forces: When one force is greater than the other, it causes motion.
🔴 Example: Pushing a stationary object to make it move.
🔹 2. Newton’s First Law of Motion (Law of Inertia)
“An object remains at rest or in uniform motion unless acted upon by an unbalanced external force.”
- A body will not change its state until a force acts on it.
- This law introduces the concept of inertia.
🔹 3. Inertia and Mass
- Inertia: The natural tendency of an object to resist a change in its state of motion or rest.
- Mass is a measure of inertia.
🔸 Heavier objects have more inertia.
🔸 Example: It’s harder to push a car than a bicycle.
🔹 4. Newton’s Second Law of Motion
“The rate of change of momentum of an object is directly proportional to the applied force and takes place in the direction of the force.”
Formula:
Where:
- F = Force
- m = Mass
- a = Acceleration
➡️ Greater the force, greater the acceleration (if mass is constant).
➡️ This law helps calculate force.
🔹 5. Newton’s Third Law of Motion
“For every action, there is an equal and opposite reaction.”
- Forces always occur in pairs.
- The action and reaction forces act on different bodies.
🟢 Example: Gun recoils when a bullet is fired.
🔹 6. Law of Conservation of Momentum
“The total momentum of a system remains constant if no external force acts on it.”
Formula:
Where:
This law is useful in collisions and explosions.
📘 Important Definitions
🧠 Examples and Activities
- A hockey ball remains at rest until a stick hits it (First Law).
- Car seat belts: Stops you when car stops suddenly (Inertia).
- Recoiling of gun (Third Law).
- Jumping from a boat pushes the boat backwards (Action-Reaction).