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“EnergyTransformations”
Energy is a measure of the ability to do work.
SI Unit for energy: Joule (J) There are two main categories of
energy, nonmechanical and mechanical energy.
Nonmechanical energy is small scale (meaning the scale of atoms).Examples of NME
include: thermal/heat, electromagnetic, nuclear, electric, sound, and chemical.
Chemical Energy: Energy associated with both the
making and breaking of chemical bonds.
Nuclear Energy: Energy that binds the nucleus of an atom
together. Can be released through nuclear fission or fusion.
Electromagnetic Energy: Form of energy made from electrical and
magnetic waves and packets of energy called photons.
Sound Energy: Energy that travels in waves by
vibrating molecules in a medium.
Electrical Energy: Energy associated with the flow of
electrons through wires or other conducting materials.
Thermal/Heat Energy:
Energy associated with the average kinetic energy of atoms or molecules.
Heat energy can be transferred in three ways:
Conduction Convection Radiation
Mechanical energy is composed of 2 types: GPE (gravitational potential energy) and KE (kinetic energy). ME is large scale meaning you can SEE it.
Potential Energy is the stored energy resulting from the relative positions of objects in a system.
There are two types:
Elastic Potential Energy
Gravitational Potential Energy
GPE (J) = mass (kg) x free-fall acceleration (9.8 m/s2) x height (m)
GPE = mghg = 9.8 m/s2
GPE
(m x g x h)
Kinetic Energy is the energy of a moving object due to its motion.
Kinetic Energy (J) = ½ x mass (kg) x speed2
([m/s]2)
KE = 1/2mv2
KE
(.5 x m x v2)
KE’s equation shows us that two main things affect KE:MassSpeed
Mass: As an objects mass increases, so does its KE.
I have a BIG kinetic energy
when I’m moving!I have a
SMALL kinetic energy
when I’m moving!
Speed: As an object’s speed increases, so does its KE. So as any object falls, its KE increases.
Penny off of the Empire State Building
Calculate the gravitational potential energy of a 1200 kg car at the top of a hill that is 42 m high.
GPE = ?m = 1200 kgg = 9.8 m/s2
h = 42 mGPE = m x g x hGPE = 1200 x 9.8 x 42GPE = 493,920 J
GPE
(m x g x h)
If a penny is sitting at the edge of a building with a mass of 0.0005 kg and a gravitational potential energy of 0.147, How tall is the building?
GPE = 0.147 Jm = 0.0005g = 9.8 m/s2
h = ?h = GPE / (m x g)h = 0.147 / (0.0005 x 9.8)h = 0.147 / (0.0049)h = 30 m
GPE
(m x g x h)
What is the kinetic energy of a 44 kg cheetah running at 31 m/s?
KE = ? m =
44 kg v =
31 m/s v2 =
961 (m/s)2
KE = .5 x m x v2
KE = (.5)(44)(961)KE = 21,142 J
KE
(.5 x m x v2)
A bowling ball traveling 2.0 m/s has 16 J of kinetic energy. What is the mass of the bowling ball in kilograms?
m = ? KE =
16 J v =
2 m/s v2 =
4 (m/s)2
m = KE / (.5 x v2)m = 16 / (.5 x 4)m = 16 / (2)m = 8 kg
KE
(.5 x m x v2)
A 35 kg child has 190 J of kinetic energy after he sleds down a hill. What is the child’s speed at the bottom of the hill?
v = ? v2 = ?
KE = 190 Jm = 35 kg
v2 = KE / (.5 x m)v2 = 190 / (.5 x 35)v2 = 190 / (17.5) v2 = 10.9v = 3.3 m/s
KE
(.5 x m x v2)
√
The Law of Conservation of Energy says that energy cannot be created or destroyed, it can only change forms.
A perpetual motion machine is a machine designed to keep going forever without any input of energy. This means ALL of the energy put into the machine
stays in the machine perpetually (forever). It’s a perfect model of the law of conservation
except it’s
IMPOSSIBLE!!!!
IMPOSSIBLE!!!!
Energy is constantly Changing forms!
Energy is constantly Changing forms!
Potential energy can be transformed into kinetic energy and vice versa.
Example: As a roller coaster is pulled up to the
top of the first hill, the mechanical energy is stored as gravitational potential energy.
As it goes down the other side of the hill, the roller coaster picks up speed, transforming the potential energy to kinetic energy.
Roller Coaster Physics Design Your Own Roller Coaster
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