Unit 5 – Lecture 1

Energy Energy – the ability to do work the ability to cause change measured in joules symbol: [as in.. E = mc 2 ] E

Energy Two descriptions: Potential Energy stored energy [due to position or condition] Kinetic Energy energy of motion / released energy

Potential Energy Three Types: Elastic PE energy stored by something that can stretch or compress [rubber band or spring]

Potential Energy Three Types: Chemical PE energy stored in chemical bonds

Potential Energy Three Types: Gravitational PE energy stored because of position above earth’s surface

Potential Energy Gravitational PE: PE gravitational = mass * accel. of gravity * height PE gravitational = m g h Remember, g = 9.8 m/s 2

Potential Energy Gravitational PE: so…what’s the unit? PE gravitational = m g h PE gravitational = kg * (m/s 2 ) * m PE gravitational = N * m PE gravitational = Joules

Kinetic Energy Kinetic Energy – released by an object by its motion depends on the mass and speed of an object KE = ½ * mass * velocity 2 KE = ½ m v 2

Kinetic Energy Kinetic Energy – released by an object by its motion So…what’s the unit? KE = ½ * mass * velocity 2 KE = (kg) * (m 2 /s 2 ) KE = Joules

Potential or Kinetic Energy? a bowling ball rolling down a lane a sandwich a ball being thrown in the air in a projectile path a gallon of gasoline a car battery a lawnmower mowing the lawn a moving baseball