1. What is Energy?

Energy is the ability to do work. It exists in different forms and can be transferred or transformed from one form to another.

✅ Key Concept:

• Energy allows objects to move, change shape, or produce heat and light.
• Energy is measured in Joules (J), the same unit as work.

2. Types of Energy

Energy exists in many forms, but the two main categories are:

🔹 Kinetic Energy (KE) – Energy of Motion

• Any moving object has kinetic energy.
• The faster and heavier an object, the more kinetic energy it has.

✅ Formula for Kinetic Energy:

KE=12mv2KE = frac{1}{2} m v^2KE=21​mv2

Where:

• $KE$ = Kinetic Energy (Joules, J)
• $m$ = Mass of object (kg)
• $v$ = Velocity (m/s)

📌 Example:
A 2 kg ball moving at 3 m/s has:

KE=12×2×32=9JKE = frac{1}{2} times 2 times 3^2 = 9 JKE=21​×2×32=9J

So, the kinetic energy of the ball is 9 Joules.

🚀 Real-Life Examples of Kinetic Energy:

• A running person.
• A moving car.
• A falling apple.

🔹 Potential Energy (PE) – Stored Energy

Potential energy is stored energy due to an object’s position or state.

📌 Two Common Types of Potential Energy:

1️⃣ Gravitational Potential Energy (GPE)

• Energy stored due to an object’s height above the ground.
• The higher and heavier the object, the more GPE it has.

✅ Formula for Gravitational Potential Energy:

$$PE=mgh$$

Where:

• $PE$ = Potential Energy (Joules, J)
• $m$ = Mass (kg)
• $g$ = Gravity (9.8 m/s²)
• $h$ = Height (m)

📌 Example:
A 5 kg book on a shelf 2 meters high has:

$$PE=5\times 9.8\times 2=98J$$

So, the book has 98 Joules of gravitational potential energy.

🚀 Real-Life Examples of Gravitational Potential Energy:

• Water in a dam (before falling).
• A stretched bow before releasing an arrow.
• A roller coaster at the highest point.

2️⃣ Elastic Potential Energy

• Energy stored in stretched or compressed elastic materials.
• Example: A stretched rubber band or a compressed spring.

3. Energy Transformations

Energy can change from one form to another:

📌 Examples of Energy Transformation:

• A falling apple: Potential energy → Kinetic energy.
• A car moving: Chemical energy (fuel) → Kinetic energy.
• A flashlight: Chemical energy (battery) → Electrical energy → Light energy.

4. Key Takeaways

✔ Energy is the ability to do work.
✔ Kinetic energy is the energy of motion.
✔ Potential energy is stored energy due to position or condition.
✔ Energy can be transformed from one type to another.