Energy Conversion and Conservation

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Transcript Energy Conversion and Conservation

ENERGY CONVERSION AND
CONSERVATION
Review - Work
 Work is done when a force acts on an
object in the direction the object moves.
 Work = Force x Distance
 W=FxD
 The joule (J) is the SI unit of work.
Review - Power
 Power is the rate of doing work.
 Power = Work / Time
 P = W/t
 The SI unit of power is the watt (W)
Review - Energy
 Work causes a change in the energy
of a system.
 The two main types of energy are:
 Kinetic
 potential
Review – Kinetic Energy
 Kinetic energy depends on motion
and is measured in joules (J).
 KE = ½ mv2
 v = velocity
Review – Potential Energy
 Gravitational Potential Energy
depends on height and is measured in
joules (J).
 PE = mgh
 h = height
 g = acceleration due to gravity 9.8m/s2
Energy Conversion
 Energy can be converted from one
form to another.
 The process of changing energy from
one form to another is energy
conversion.
 EX: Rubbing hands – kinetic energy to
thermal energy.
Conservation of Energy
 When energy changes from one form
to another, the total energy remains
unchanged.
 The law of conservation of energy
states that energy cannot be created
or destroyed.
Energy Conversions
 The gravitational potential energy of an
object is converted to the kinetic energy of
motion as the object falls.
 EX: sky diving
 The kinetic energy of motion is converted to
gravitational potential energy when an
object is gaining height.
 EX: pole vaulting
Energy Conversion in a
Pendulum
Energy Conversion
 Your beginning energy must equal your
ending energy. This allows us to say that:
 (KE + PE)beginning = (KE + PE)end
 Which means you can set kinetic energy
equal to potential energy.