Energy (NRG)

(p 208) There are many forms of energy: mechanical, thermal, electrical, nuclear One form of energy can be converted to other forms When energy is changed to different forms, work is done

Mechanical Energy Any time you store energy it gains the potential to do work. Mechanical energy is the energy of an object due to it position or motion. Mechanical NRG has two components Potential NRG – known as stored NRG Kinetic NRG – the energy of motion

Potential Energy (p208) Potential energy is stored energy due to position Potential Energy (PE) can be stored many ways: Gravitation: Ep=m×g×h or Ep = Fd Elastic: Ep = ½ kx2 Chemical (batteries) Thermal Nuclear

Gravitational Potential NRG This boulder has potential energy due to position. It has the potential to crush the student below. It also has the ability to do work (by changing the students shape)

Gravitational Potential NRG When work is done against gravity, this work is stored in the system as: Gravitational Potential Energy (GPE). GPE is dependent on: the force acting on the object (Force of gravity) the vertical displacement of the object (its height)

Gravitational Potential NRG (p 209) Gravitational potential energy is always measured relative to some reference point Formula: Ep = mgh or Ep=Fd Unit: Joule (J) as Ep is a type of work See example problems p 209

Kinetic NRG (p 212) Kinetic energy is the energy of motion. When work is done accelerating a object from rest it becomes kinetic energy. Kinetic energy formula: Ek=½mv2 Units: Joules (J) See example probs p 213