Energy
Energy & Work
•Closely related
•Energy: ability to do work
•Work: transfer of energy
• Both measured in Joules
Energy Types
1. Kinetic Energy: Energy in motion
2. Potential Energy: Stored energy (not moving)
• depends on position or condition of object
Examples of KE
Examples of PE
FirecrackerBoulder on top of cliff
battery
Calculating KE
KE = ½ mv2 m = mass v = velocity
• Which increases kinetic energy more: doubling the mass or doubling the velocity?
Gravitational PE
• PE that depends on object’s height, and weight
G.P.E. = mgh
m = mass g = 9.8 m/s2
h= height.Which will have greater GPE: a rock on a 3 story ledge or a rock on a 20 story ledge?
Mechanical Energy
• PE Converts to KE and vice versa
• Mechanical Energy = KE + PE– Total energy
• Skier• Roller Coaster• Dart
Energy conversions
•Law of conservation of energy:
•Energy cannot be created or destroyed, only converted from one form to another