Energy
In contrast to matter, energy has no mass and does not take up space. It can be measured
only by its effects on matter. We commonly define energy as the ability to do work or to put
matter into motion. When energy is actually doing work (moving objects), we refer to it as
kinetic energy.
Kinetic energy is displayed in the constant movement of the tiniest particles of matter
(atoms) as well as in larger objects, such as a bouncing ball. When energy is inactive or
stored (as in the batteries of an unused toy), we call it potential energy. All forms of energy
exhibit both kinetic and potential work capacities.
Actually, energy is a physics topic, but it is difficult to separate matter and energy. All living
things are built of matter, and to grow and function they require a continuous supply of
energy.
Thus, matter is the substance, and energy is the mover of the substance. Because this is so,
let’s take a brief detour to introduce the forms of energy the body uses as it does its work.
Forms of Energy
• Chemical energy is stored in the bonds of chemical substances. When the bonds are
broken, the (potential) stored energy is unleashed and becomes kinetic energy (energy in
action).
For example, when gasoline molecules are broken apart in your automobile engine, the
energy released powers your car.
In like manner, the chemical energy harvested from the foods we eat “runs” all body
activities.
• Electrical energy results from the movement of charged particles. In your house, electrical
energy is the flow of electrons along the wiring. In your body, an electrical current is
generated when charged particles (called ions) move across cell membranes. The nervous
system uses electrical currents called nerve impulses to transmit messages from one part of
the body to another.
• Mechanical energy is energy directly involved in moving matter. When you ride a bicycle,
your legs provide the mechanical energy that moves the pedals. We can take this example
one step further back: As the muscles in your legs shorten, they pull on your bones, causing
your limbs to move (so that you can pedal the bike).
In contrast to matter, energy has no mass and does not take up space. It can be measured
only by its effects on matter. We commonly define energy as the ability to do work or to put
matter into motion. When energy is actually doing work (moving objects), we refer to it as
kinetic energy.
Kinetic energy is displayed in the constant movement of the tiniest particles of matter
(atoms) as well as in larger objects, such as a bouncing ball. When energy is inactive or
stored (as in the batteries of an unused toy), we call it potential energy. All forms of energy
exhibit both kinetic and potential work capacities.
Actually, energy is a physics topic, but it is difficult to separate matter and energy. All living
things are built of matter, and to grow and function they require a continuous supply of
energy.
Thus, matter is the substance, and energy is the mover of the substance. Because this is so,
let’s take a brief detour to introduce the forms of energy the body uses as it does its work.
Forms of Energy
• Chemical energy is stored in the bonds of chemical substances. When the bonds are
broken, the (potential) stored energy is unleashed and becomes kinetic energy (energy in
action).
For example, when gasoline molecules are broken apart in your automobile engine, the
energy released powers your car.
In like manner, the chemical energy harvested from the foods we eat “runs” all body
activities.
• Electrical energy results from the movement of charged particles. In your house, electrical
energy is the flow of electrons along the wiring. In your body, an electrical current is
generated when charged particles (called ions) move across cell membranes. The nervous
system uses electrical currents called nerve impulses to transmit messages from one part of
the body to another.
• Mechanical energy is energy directly involved in moving matter. When you ride a bicycle,
your legs provide the mechanical energy that moves the pedals. We can take this example
one step further back: As the muscles in your legs shorten, they pull on your bones, causing
your limbs to move (so that you can pedal the bike).
