Laws of Motion

📖 Definition

The Laws of Motion, proposed by Sir Isaac Newton in 1687, are three principles that describe how objects behave when forces act upon them. These laws laid the foundation for classical mechanics.

🥇 First Law of Motion – Law of Inertia

“An object at rest stays at rest, and an object in motion continues in uniform motion unless acted upon by an external force.”

✅ Explanation:

• This law explains inertia, the natural tendency of objects to resist changes in motion.
• It means that motion doesn’t require force, only changes in motion do.

🧠 Real-life Examples:

• A glass stays on a table unless pushed.
• Passengers lurch forward in a car when brakes are applied suddenly—because their bodies want to remain in motion.

🥈 Second Law of Motion – Law of Acceleration

“The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.”

🧪 Formula: F = m × a

• F = Force
• m = Mass
• a = Acceleration

✅ Explanation:

• This law links force, mass, and acceleration.
• Heavier objects need more force to accelerate.

🧠 Real-life Examples:

• It takes more effort to push a loaded trolley than an empty one.
• A soccer ball moves faster when kicked with more force.

🥉 Third Law of Motion – Action & Reaction

“For every action, there is an equal and opposite reaction.”

✅ Explanation:

• This law applies to interactions between two objects.
• Forces always come in pairs: one object exerts a force, the other exerts a reaction force.

🧠 Real-life Examples:

• When you jump, your legs push the ground down; the ground pushes you up.
• Rocket propulsion works by expelling gases downward; the rocket moves upward.

🧲 2. Forces

📖 Definition

A force is an influence that causes an object to change its motion, shape, or state of rest. It is a vector quantity, having both magnitude and direction.

🧮 Formula:

F = m × a (also from Newton’s Second Law)

🔍 Types of Forces:

1. Gravitational Force – Attraction between two masses (e.g., Earth pulling objects down).
2. Frictional Force – Resistance between two surfaces in contact.
3. Normal Force – Perpendicular support force from a surface.
4. Tension Force – Force through a string, rope, or cable.
5. Applied Force – Force directly exerted on an object by a person or tool.
6. Air Resistance – Opposes motion of objects through air.
7. Magnetic and Electric Forces – Due to magnetic fields or electric charges.

🧠 Examples:

• Pushing a chair: you apply an applied force; the floor offers friction.
• Object falling: gravity pulls it down; air resistance slows it.

🌍 3. Gravity

📖 Definition

Gravity is the universal force of attraction acting between all matter. On Earth, it gives weight to physical objects and causes them to fall when dropped.

🌌 Newton’s Law of Universal Gravitation:

“Every particle in the universe attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.”

🧮 Formula:

F = G × (m₁ × m₂) / r²

• F = gravitational force
• G = gravitational constant (6.674 × 10⁻¹¹ N·m²/kg²)
• m₁, m₂ = masses
• r = distance between them

🧠 Examples:

• Tides on Earth caused by gravitational pull from the Moon.
• Planets orbiting the Sun due to gravitational attraction.

🔋 4. Energy

📖 Definition

Energy is the capacity to do work. It exists in different forms and is conserved in physical processes (First Law of Thermodynamics).

⚡ Forms of Energy:

1. Kinetic Energy – Energy of motion
   • KE = ½mv²
2. Potential Energy – Stored energy due to position or condition
   • PE = mgh
3. Thermal Energy – Heat energy from particle motion
4. Chemical Energy – Stored in chemical bonds
5. Electrical Energy – Movement of electrons
6. Nuclear Energy – Energy stored in atomic nuclei
7. Radiant Energy – Light or electromagnetic radiation

🔄 Law of Conservation of Energy

“Energy can neither be created nor destroyed; it can only change form.”

🧠 Examples:

• Waterfall: water at the top has potential energy → converts to kinetic energy as it falls.
• Battery powering a fan: chemical energy → electrical → mechanical.
• Burning wood: chemical energy → heat + light.

🧱 5. Matter

📖 Definition

Matter is any substance that has mass and takes up space (volume). It is made up of atoms and molecules.

🧪 States of Matter:

🔬 Atomic Structure:

• Atom = smallest unit of matter
• Composed of:
  • Protons (+)
  • Neutrons (neutral)
  • Electrons (−)

🧠 Examples:

• Water (H₂O) is made of two hydrogen atoms and one oxygen atom.
• Air is a mixture of gases (nitrogen, oxygen, argon, etc.).