Energy is something that does something to matter.
Energy
Energy is the ability to do work - make things move.
does not have mass or volume (matter)
described by the things that it does - its
interaction with matter
can move by itself or through matter
measured in joules (J)
E=MC2
James Prescott Joule
1818-1889
Newton’s Second Law: F=ma; force = mass times acceleration
A force (f) is any push or pull or any influence
that can change the motion of an object such as
gravity. Forces are measured in the metric system by a
unit called a newton (N). Weight is the force due to
gravity. 1 newton equals a force that will give a 1
kilogram mass an acceleration (a = m/s2) of 1 meter per
second per second (kg)(m)/(s2). Instead of saying: kg×m/s2
momentum = mass times velocity
We say: N
Work (W) is defined as force that acts over a
distance, or the movement of an object from one
location or position to another. Work equals force
times distance. The equation for work is: W = f × d
Distance (d) in the metric system is measured in
meters (m) and force is measured in newtons (N).
Instead of using the unit n×m, work is measured using
the metric unit joule (J).
Ex. If a 500N box is lifted 2 meters, how much work has
been done? 500N × 2m = 1000J
J = newton × meter Work can also be defined as the change (Δ) in kinetic energy or
Metric unit:
English unit: calories
the change (Δ) in potential energy.
1 BTU = 255 calories = 1055J
Energy - 2
Each time work is done energy is transferred or
given by one object to another that allows it to do
work. So work is also understood to be the transfer of
energy. When a certain amount of work is done, the
same amount of energy is involved. Energy is therefore
measured in joules just like work.
Energy can either be used right away or
stored for use later. All energy is described by
either:
1
2
3
Distance = 0
NO WORK its position / shape / chemistry or so work = 0
W=f*d
composition - Potential Energy
WORK  its motion - Kinetic Energy
These are ways that energy is measured – not types of energy!
Energy that is stored and is not being used is
called potential energy (PE). Since these objects are
not moving and are resting, there is no work being done.
Potential energy is still measured in joules because of
the object’s potential to do work. It is measured by its
1
2
3
position or shape or chemistry.
Examples:
stretched rubber band or spring
heavy object
charged battery
any type or fuel or food
tank of gasoline
sugar
Energy - 3
Weight is PE due to its position. All food and
fuel is PE due to its chemistry. A stretched spring is
PE due to its shape. PE can also be measured as weight
times height - GPE. A 10 newton object 2 meters above
= gravitational potential energy =
the ground has a PE of 20J. GPE
weight times height
Kinetic energy (KE) is energy in motion that is
being used. Work is being done. All moving objects
have kinetic energy and are doing work. The amount of
kinetic energy of an object depends on its mass and
speed. The faster an object moves or the more
massive it is, the more kinetic energy it has. Kinetic
energy is measured in joules (J) by multiplying the mass
in kilograms by the velocity squared in meters per
second, and then and dividing by two.
The equation is: KE = ½ mv2
All energy travels in waves - either through
matter or by itself in the form of electromagnetic
radiation. An energy wave that travels through matter
is called a mechanical wave. The material a wave
travels through is called a medium.