Chemistry Reference
In-Depth Information
exert a force over a distance. There are many forms of energy, including
heat, mechanical, chemical, electrical, solar, and nuclear. According to the
Law of Conservation of Energy, we can convert one form into another.
Energy is measured in units called joules, or J for short.
Gravitational Potential Energy:
The energy that an object possesses due to its mass and its height
above a reference point.
Gravitational P.E. =
mass × acceleration due to gravity × height or P.E. = mgh
When the bowling ball was lifted onto the shelf, it was given gravita-
tional potential energy. Gravitational potential energy is the stored energy
that an object possesses due to its mass and its position above a reference
point, in this case your foot. When the bowling ball fell off the shelf, its
height above the floor decreased, decreasing its gravitational potential
energy. When the bowling ball hit your foot, its height above it was zero, so
its gravitational potential energy, with reference to your foot, was zero.
Was its potential energy destroyed? No—it just changed into another form
of energy called kinetic energy.
Kinetic Energy:
The energy that an object possesses due to its mass and velocity.
Kinetic energy = 1/2 mass × velocity
2
or K.E. = 1/2 mv
2
Gravitational Potential Energy is Converted to Kinetic Energy
The ball has high gravitational
potential energy (mgh), because its
height is high. It has low kinetic
energy (1/2mv
2
), because its velocity
is low.
The ball has low gravitational
potential energy (mgh), because its
height is low. It has high kinetic
energy (1/2mv
2
), because its velocity
is high.
Figure 1-5a
