Transcript Energy - Welcome to ms

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
Calculating KE
KE = ½ mv2
m = mass
v = velocity
• Which increases kinetic energy
more: doubling the mass or doubling
the velocity?
Examples of PE
Boulder on top of cliff
battery
Firecracker
Elastic Energy
(type of potential energy)
• Energy stored in a compressed material
– Example: rubber band, spring
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?
Forms of Energy
• Mechanical Energy: Related to
motion of objects
– Ex : moving machine parts
Windmill
Engine piston
Mechanical Energy
• PE Converts to KE and vice versa
• Mechanical Energy = KE + PE
– Total energy
• Skier
• Roller Coaster
• Dart
Thermal Energy
• Related to heat
• Thermal Energy = total KE and PE
of all particles in an object
– Particles in matter are constantly
moving
Chemical Energy
(type of potential energy)
• Energy stored in chemical bonds
within a substance
Ex: Gas, food, human body, battery
Electrical Energy
• Energy of Electric Charges
Electromagnetic Energy
• Energy traveling in the form of
waves
• X-rays
Visible light
Nuclear Energy
• Energy stored in nucleus of an atom
• Nuclear Power plants convert
nuclear energy to electricity
Energy conversions
•Law of conservation of energy:
•Energy cannot be created or
destroyed, only converted from
one form to another
Impact crater in Arizona formed within past 20 yrs
Large KE of meteor converted to large amount
of thermal energy vaporizing everything in
Close proximity
Energy conversions
• Light bulb : converts electrical into
thermal and electromagnetic energy
• Compressed Spring: converts potential
to kinetic
• Burning wood: stored chemical energy
converted to thermal and
electromagnetic
Energy Conversion
in a Pendulum
If friction is ignored total
mechanical energy will remain
constant
(KE + PE)
start
= (KE + PE)end
Pendulum would swing forever!!!
Viewing a Pendulum
• Pendulum Energy Conversion