⚡ KINETIC ENERGY NOTES
1. Definition
• Kinetic Energy (KE): The energy possessed by an object due to its motion.
• Formula: KE = 1/2 m v²
• m = mass of object (kg)
• v = velocity of object (m/s)
2. Units
• SI Unit: Joule (J)
• 1 Joule = 1 kg·m²/s²
3. Types of Kinetic Energy
1. Translational KE: Due to linear motion
2. Example: A moving car
3. Rotational KE: Due to rotation around an axis
4. Example: Spinning wheel
5. Vibrational KE: Due to vibration of particles
6. Example: Molecules in a solid
4. Work-Energy Theorem
• Theorem: The work done on an object is equal to the change in its kinetic energy.
• Formula: W = ΔKE = KE_final - KE_initial
5. Relationship with Potential Energy
• Total Mechanical Energy (E) = KE + PE
• Conversion: Energy can convert from PE to KE and vice versa
• Example: A roller coaster at the top (PE) and moving down (KE)
6. Factors Affecting Kinetic Energy
1. Mass: KE is directly proportional to mass
2. Velocity: KE is proportional to the square of velocity
3. Doubling velocity quadruples KE
7. Applications
• Vehicle motion and safety
• Sports science (kicking a ball, running)
• Engineering (turbines, engines)
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• Particle physics (motion of atoms/molecules)
8. Sample Problem
• A 2 kg object moves at 3 m/s. Calculate its kinetic energy.
• KE = 1/2 × 2 × 3² = 1 × 9 = 9 J
9. Conceptual Notes
• Stationary objects have KE = 0
• Faster objects or heavier objects have more KE
• KE is scalar; it has magnitude but no direction
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