Overview
This lecture explains kinetic energy, its dependence on speed and mass, and how to calculate it using the kinetic energy formula.
What is Kinetic Energy?
- Kinetic energy is the energy an object possesses because of its motion.
- Any moving object, regardless of size, has kinetic energy.
Factors Affecting Kinetic Energy
- Kinetic energy depends on two factors: the object's speed and its mass.
- Faster objects have more kinetic energy.
- Heavier objects (with more mass) have more kinetic energy when moving at the same speed as lighter ones.
Calculating Kinetic Energy
- The formula for kinetic energy is: ( E_k = \frac{1}{2} m v^2 ).
- ( E_k ) is the kinetic energy, measured in joules (J).
- ( m ) is mass in kilograms (kg).
- ( v ) is velocity (or speed) in meters per second (m/s).
- Only the speed (( v )) is squared in the formula, not the entire expression.
Example Calculations
- Always convert mass to kilograms and speed to meters per second before calculating.
- For a 20-ton (20,000 kg) plane moving at 5 m/s: ( E_k = 0.5 \times 20,000 \times 5^2 = 250,000 ) J (or 250 kJ).
- For a 0.1-gram (0.0001 kg) particle moving at 4,000 m/s: ( E_k = 0.5 \times 0.0001 \times 4,000^2 = 800 ) J (or 0.8 kJ).
- Even a very fast, light particle may have less kinetic energy than a slow, heavy object.
Key Terms & Definitions
- Kinetic Energy — Energy due to motion.
- Mass (m) — The quantity of matter in an object, measured in kilograms (kg).
- Velocity (v) — The speed of an object in a specific direction, measured in meters per second (m/s).
- Joule (J) — The unit of energy in the metric system.
Action Items / Next Steps
- Practice using the kinetic energy formula with different masses and velocities.
- Ensure all quantities are in the correct units before calculations.