Energy Continued Unit 5 – Lecture 2

Review: PE & KE Potential Energy – “stored” E Kinetic Energy – energy of motion / “released” E

Conservation of Energy Law of Conservation of Energy: energy can neither be created nor destroyed in normal reactions energy can be changed in form from one to another initial energy = final energy energy in = energy out aka 1st law of thermodynamics

Mechanical Energy Mechanical E – total amount of PE & KE in a system as PE decreases, KE increases as PE increases, KE decreases what kind of relationship is this…direct or inverse?

Mechanical Energy Equation: MEinitial = MEfinal (PE + KE)initial = (PE + KE)final (m g h + ½ m v2 )initial = (m g h + ½ m v2 )final

Mechanical Energy ME in a pendulum:

Practice At which point… is GPE at a maximum? why? is KE at a maximum?

Practice Which of these describes E? [any] Ability to do work Ability to cause change Ability to increase energy Ability to decrease work Joules is NOT a unit for which of these? PE KE Force Work

Forms of Energy Mechanical Energy energy of an object due to its motion [kinetic E] or position [potential E]

Forms of Energy Electromagnetic E waves of mostly invisible E light energy often is converted into thermal E can be converted into chemical E through photosynthesis

Forms of Energy Chemical E stored and released in the bonds between atoms food, batteries

Forms of Energy Nuclear E stored and released from the nucleus of an atom

Forms of Energy Thermal E heat in all its forms and flows recall – exothermic & endothermic transferred through conduction, convection, & radiation

Forms of Energy Electrical E separation and movement of electrons [not really a form of E on its own – it is a combination of forms of Mechanical and Electromagnetic E]

Practice When you are watching tv, what energy conversions are taking place? Which energy transformation takes place when a match is struck against the side of a matchbox and bursts into flames? What causes you to hear something? What kind of energy is sound?