Energy. DEFINITION the ability to cause a change common measurement unit = Joule (J)
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Transcript of Energy. DEFINITION the ability to cause a change common measurement unit = Joule (J)
Energy
DEFINITION
• the ability to cause a change
• common measurement unit = Joule (J)
FORMS• energy exists in many different forms:
1. potential 2. kinetic3. mechanical4. heat5. chemical6. nuclear7. electrical8. light9. sound
(Gravitational) Potential Energy
• abbreviations: PE, GPE, and PEgravitational
• energy stored in a non-moving object due to its position, shape, or composition in a gravitational field
Kinetic Energy• abbreviation: KE
• energy of motion
• all moving objects have kinetic energy
Mechanical Energy
• total potential energy & kinetic energy of an object
• ME = PE + KE
Heat• Energy that moves from hot objects to cooler
ones
Chemical Energy• energy stored in chemical bonds
Nuclear Energy
• Energy stored in the nucleus of an atom
Electrical Energy
• Energy of moving electrons
Light Energy• Energy contained in electromagnetic waves
Sound Energy
• Energy produced by vibrating objects
Potential Energy Word Problems
A 4 kg rock is sitting on a 3 m ledge.
How much gravitational potential energy does it have?
GIVENS: m = 4 kg h = 3 m g = 9.8m/s2
UNKNOWN: PE
EQUATION: PE = mgh
SUBSTITUTION: PE = (4 kg) x (9.8m/s2) x (3 m)
SOLUTION: 117.6 J
Kinetic Energy Word Problems
A 3 kg ball is rolling at a velocity of 2 m/s.
How much kinetic energy does it have?
GIVENS: m = 3 kg v = 2 m/s
UNKNOWN: KE
EQUATION: KE = ½ mv2
SUBSTITUTION: KE = ½ (3kg)(2m/s)2
SOLUTION: 6kgm/s2 = 6 J
LAW of CONSERVATION of ENERGY
Energy cannot be created or destroyed, BUT
it can be transferred from one object to another
AND it can be changed, or converted, from one
form to another
Energy Transfer
• Occurs when one object passes some of its energy to another object
• First object loses energy; second object gains energy
• 3 main ways: conduction, convection, and radiation
Conduction• Energy is transferred within an object or between objects that are touching
• As particles in objects collide, their energy is transferred
Convection• Fluids (liquids & gases) transport energy from one place to another
• Forms convection currents
Radiation• transfer of energy through electromagnetic waves
• radiation is felt as energy is absorbed by a material
Energy Conversions• AKA energy transformations
• Change of one form of energy into another
example
Electric Fan
• Electrical → kinetic
• When you plug in the fan, electricity causes the blades to move