I. Energy and Work (p.124-131) Energy Work Conservation of Energy Ch. 5 - Energy I. Energy and Work (p.124-131) Energy Work Conservation of Energy

A. Energy ENERGY THERMAL The ability to cause change. MECHANICAL internal motion of particles ENERGY MECHANICAL NUCLEAR motion of objects changes in the nucleus ELECTRICAL joules (J) CHEMICAL motion of electric charges bonding of atoms

A. Energy Kinetic Energy (KE) energy in the form of motion depends on mass and velocity 80 km/h 50 km/h Which has the most KE? Which has the least KE? 80 km/h truck 50 km/h motorcycle

A. Energy Potential Energy (PE) stored energy depends on position or configuration of an object Which boulder has greater gravitational PE? What other ways can an object store energy?

W = Fd B. Work Work transfer of energy through motion force exerted through a distance W = Fd W: work (J) F: force (N) d: distance (m) 1 J = 1 N·m Distance must be in direction of force!

B. Work Brett’s backpack weighs 30 N. How much work is done on the backpack when he lifts it 1.5 m from the floor to his back? GIVEN: F = 30 N d = 1.5 m W = ? WORK: W = F·d W = (30 N)(1.5 m) W = 45 J F W d

d B. Work W F GIVEN: m = 40 kg d = 1.4 m - during d = 2.2 m - after A dancer lifts a 40 kg ballerina 1.4 m in the air and walks forward 2.2 m. How much work is done on the ballerina during and after the lift? GIVEN: m = 40 kg d = 1.4 m - during d = 2.2 m - after W = ? WORK: W = F·d F = m·a F =(40kg)(9.8m/s2)=392 N W = (392 N)(1.4 m) W = 549 J during lift No work after lift. “d” is not in the direction of the force. F W d

C. Conservation of Energy Law of Conservation of Energy Energy may change forms, but it cannot be created or destroyed under ordinary conditions. EX: PE  KE mechanical  thermal chemical  thermal

C. Conservation of Energy PE  KE View pendulum animation. View roller coaster animation.

C. Conservation of Energy Mechanical  Thermal View rolling ball animations. View skier animation.