1. Unit 5: Energy Intro to energy notes

2. What is energy? Energy is the ability of a physical system to do work Energy takes many forms – The movement of objects – Stored in bonds of wood, oil and food – Sound waves moving through the air – Electromagnetic waves from cell phones

3. First, some review Speed (velocity) = distance traveled over time Distance is measured in meters (m) Time is measured in seconds (s) The formula for speed (velocity) is Speed = meters / seconds Speed =m/s

4. More review Acceleration is a change in velocity with each passing second Acceleration = (Meters/second)/second Acceleration = m/s/s Acceleration = m/s 2 Gravity is measured as an acceleration! Gravity on earth = 9.8 m/s 2

5. Mass VS. Weight Mass – The amount of matter in an object Weight – The effect of gravity on the mass of an object If you went to a different planet, would your mass or your weight change?

6. Force A force is a push or a pull Formula: Force = Mass * Acceleration due to gravity F= MA F = Kg *m/s 2 The metric unit of force is the Newton

7. Weight is a force Your weight is gravity’s effect on your mass Weight = your mass * acceleration from gravity Weight = Kg * m/s 2 Newtons = Kg * m/s 2

8. Work is a force exerted over a distance Work = Force * Distance Work = N * m Work = Kg * m/s 2 * m Work = Kg * m 2 /s 2 The unit for work is a Joule Joule = Kg * m 2 /s 2

9. Potential (mechanical) energy The ability of an object to exert a force through movement PE = Mass * gravity * height PE = m*g*h PE = (kg)(m/s 2 )(m) PE = kg. m 2 /s 2 Units for potential energy?

10. Kinetic energy Energy associated with the motion of an object KE = ½* mass*velocity 2 KE = ½ * Kg *(m/s) 2 KE = ½ Kg*m 2 /s 2 Units for kinetic energy?

11. Important units Speed/velocity: m/s Acceleration: m/s 2 Mass: Kg Force/Weight: Newtons (Kg*m/s 2 ) Work: Joules (kg*m 2 /s 2 )

12. Back to ENERGY! Energy is the ability to do work Energy is measured in Joules and calories calorie – The energy required to raise the temperature of 1 mL of water by 1 0C – This is very small Calorie – Aka: Food calorie, kilocalorie – 1000 calories