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Ch. 5 - Energy I. Energy & Work (pp. 256-332) Energy Work Conservation of Energy Thermal Energy Make a table in your notes Type of Energy Description Examples A. Energy Types THERMAL HEAT ELECTROMAGNETIC internal energy of transfer of energy b/c of a El’c and mag’c energy in the difference in temp. form of waves particles NUCLEAR ENERGY MECHANICAL Energy released b/c of changes in the nucleus (fission or fusion) The ability to cause change. Energy of moment/ potential movement CHEMICAL Measured in joules (J) PE held in bonds between atoms SOUND Mechanical wave through medium RADIANT/LIGHT “visible;” emitted by moving charged particles ELECTRICAL motion of electric charges A. Energy Potential Energy (PE = mgh) stored energy depends on position or configuration of an object • Which boulder has greater gravitational PE? • What other ways can an object store energy? A. Energy Kinetic Energy (KE = ½ mv2) energy in the form of motion depends on mass and velocity • Which has the most KE? 80 km/h truck • Which has the least KE? 50 km/h motorcycle 80 km/h 50 km/h 80 km/h A. Energy Problems Calculate the KE of a 40 kg girl running on a track at 15 m/s. Calculate the gravitational PE of a 50 kg boy at the top of the stadium (12.5 m). B. Work Work transfer of energy through motion force exerted through a distance W = Fd W: F: d: work (J) force (N) 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 W F d B. Work 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=? W F d 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. 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.