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