CHAPTER 15: ENERGY!

Energy: Measured in joules! The ability to do work Work = Force x distance Measured in joules!

ENERGY

Forms of Energy: Kinetic: energy of movement (depends on mass and velocity)

Forms of Energy: Potential: energy of position - gravitational: depends on mass, height and acceleration due to gravity - elastic: depends on ability to be stretched or compressed - chemical: stored in bonds - electrical: associated with charge - nuclear: stored in the atomic nucleus - electromagnetic: waves (light/rays/sound)

The Law of Conservation of Energy Energy is never created or destroyed – it is transformed from one form to another. (PE+KE)Beginning = (PE+KE)End

The Law of Conservation of Energy Often, kinetic energy will be transformed into thermal energy, via FRICTION. This is the reason we always LOSE efficiency when work is done!

Calculating Kinetic Energy m = mass (kg) v = velocity (m/s) KE = kinetic energy (Joules)

Calculating Kinetic Energy What is the kinetic energy of a 75-kg student running at a speed of 3 m/s?

Calculating Potential Energy m = mass (kg) g = acceleration due to gravity (9.8 m/s2) h = height (m) PE = potential energy (Joules)

Calculating Potential Energy A mover carries a television with a mass of 62 kg a distance of 18 m up the stairs. How much potential energy does the TV have? PE = (62)(9.8)(18) = 10,937 J

The Law of Conservation of Energy If 2500-kg roller coaster car begins its descent from 500 m above the first hill, what is its kinetic energy at the bottom of that hill? PE = (2500)(9.8)(500) = 12,250,000 J = KE!