Few explanations of science concepts are given in the text as you
will probably go through the book in a different order than it is
presented here. When you read words in the text, it is assumed that
you know the concept. If you dont, or if you need a refresher,
come to this section and review the science concept.
The purpose of this book is not to replace existing physics and
chemistry books. For more detailed explanations, any simple high
school text will make things clearer and give good examples.
Newtons Three Laws
Isaac Newton identified three physical laws that have been influencing
man, the earth, and the universe from the beginning of time. They
The law of inertia says that an object continues in its state
of rest or continues in uniform motion in a straight line until
it is acted upon by an outside force. Something at rest will tend
to stay at rest. Something in motion will tend to stay in motion.
Put a 3 x 5 card over the top of a glass or cup. Put a penny in
the center of the card. Snap the card with your finger. What happens
to the penny? This demonstrates inertia of an object at rest.
Travel in a boat, four wheeler, or snowmachine at a constant speed.
Throttle down or put on the brakes. Why does your body go forward
when the machine slows down? This demonstrates that a object in
motion (your body) will stay in motion until acted upon by an outside
You notice that the law of inertia says that an object continues
in uniform motion in a straight line. When an object is spun around,
like a model airplane on a string, it has a tendency to go in a
straight line, pulling against the string. The force of an object
to fly away from the center when spun in a circle is called centrifugal
force. Centrifugal means fly away from center.
F = MA
The second law that Newton described was F = MA.
Force = Mass x Acceleration.
If an object is accelerated or decelerated, the force causing
that change can be measured by multiplying the mass times the rate
of acceleration or deceleration.
We deal with forces all day, every day. You travel thirty miles
per hour on a four wheeler. You stop. Are you hurt? That depends
on the rate of deceleration. If you stop in ten seconds you are
not hurt. If you stop instantly when the four wheeler hits a tree,
you very well might be.
For a planing boat, there is a critical point where the rate water
is pushed away is high enough that the water seems to become solid
and the boat gets on step, that is, on top of the water
rather than plowing through it.
Mass vs Weight
The mass of something and the weight are different. The mass of
something refers to how much matter is in the object. It has just
as much mass in outer space as it does on earth. The weight refers
to how much gravity is pulling on something. An object could weigh
ten pounds here on earth, weigh nothing in outer space, yet the
mass would be the same in both places.
As simple scientists here on earth, we often inaccurately refer
to them as the same.
Acceleration is defined as distance (feet) per second squared.
Herein is one of the most important concepts in all science. With
many forces, as one variable is increased, the result increases
in the same proportion. With equations that involve acceleration,
the result is squared. When a variable is increased, the result
is squared or reduced by the square.
Lets look at an example. An object with a mass of ten is
at rest. It is accelerated to ten feet per second.
In one case, it is accelerated to that speed in four seconds.
In another case it is accelerated in twice that time, eight seconds.
Is the force cut by one-half because the time of acceleration
is doubled? NO! The force required is reduced by one-quarter.
This explains why there is a very critical speed at which an airplane
will either fly or stall. The rate at which the air is pushed out
of the way is squared. The difference in lift at fifty-six mph and
sixty mph can be great.
A = R
The third law that Newton described was A = R. Every action has
an equal and opposite reaction. As a bullet hits an animal, the
force against the animal by the bullet is acknowledged. But the
animal also exerts an equal force on the bullet. It is slowed down
from very high velocity to zero velocity.
A woodsman swings an axe at a tree. The axe exerts a force against
the tree. The tree exerts a force against the axe.
Each action has and equal and opposite reaction. In the above
examples the reaction is damaged flesh and severed wood.
Friction is the resistance to motion between two surfaces that
are in contact. We spend much of our lives trying to increase or
decrease friction. Without friction it is impossible to light a
match. If we dont avoid friction, a chainsaw might not last
an afternoon. I have always regarded the understanding of friction
as most important in the North. Since the wheel is very impractical
without roads and hard surfaces, sleds and boats have been pushed
and pulled in their respective seasons for thousands of years. Friction
has made fires, hindered motion, and inserted itself into traditional
life in a multitude of ways.
Friction has two causes:
- Molecular attraction between two surfaces. The molecules actually
form a slight electromagnetic bond with each other.
- Rough surfaces interlock with each other. The rough spots on
one surface mesh with the rough spots on the other. Material is
ripped from each surface, and there is a constant chattering between
the two materials.
There are two types of friction:
- Static friction. Two surfaces are in contact, but are
not moving against each other.
- Sliding (kinetic) friction. Two surfaces are in contact
and are moving against each other.
Static friction is greater than kinetic friction. When you get
a sled going on the snow, there are two things you are overcoming:
As the sled is moving, inertia is overcome. There is kinetic friction,
but kinetic friction is much less than static friction. It is easier
to keep a sled moving than it is to get it in motion.
Pressure and weight influence friction
While the friction of two surfaces can be measured, the friction
can be increased or decreased by increasing or decreasing the weight
or pressure between the two. If you drag a file cabinet across the
floor, the friction will be reduced if the drawers are removed to
reduce the pressure between the two sliding surfaces.
Different surfaces have different amounts of friction. An unpeeled
log is very hard to drag through the woods. The same log peeled
will drag easily. High and low friction.
There are times when we want to increase friction. We put sand
or sawdust in paint on stairs to roughen the surface so we wont
slip. Brakes on snowmachines are designed to induce friction to
slow down the machine. The kinetic energy of the machine is changed
to heat energy in the brake.
There are times when we try to avoid friction like in bearings
and on sled runners.
Byproducts of friction
Friction is a force acting against motion. There is no movement
without friction on the earth. Some movements might minimize friction,
but all movements involve some amount. The byproducts of friction
are mostly heat but occasionally sound. Rub your hands together
when they are cold. Do they get warm? This is a product of friction.
Listen to a fishwheel that isnt lubricated. Can you hear it
groan? This sound is the product of friction.
Surface area is simply the area of an object that is exposed.
A hand that is closed and one that is open are not different in
any way except that the surface area is different. The mass, chemical
composition, density, etc. are the same in both hands. Mittens and
gloves cover the same hand, but their surface area is different.
Understanding surface area is important to us for three main reasons.
1. Heat transfer and loss are greatly influenced by the surface
area exposed to the heat differences. A chainsaw head has fins to
increase surface area to get rid of heat. A winter traveler curls
his hand in his mittens to reduce the surface area that can lose
2. The pressure exerted on a surface is described in terms of
pounds per square inch. How many square inches is the force being
exerted upon? Snowshoes increase the surface area a persons
weight is distributed upon. A knife decreases the surface area a
workers efforts are distributed upon.
3. The surface area that is exposed where a chemical reaction
can take place often determines how rapidly the reaction can occur.
When we make shavings to start a fire in the morning, we are simply
increasing the surface area upon which combustion can occur.
Forms of Energy
There are six forms of energy available to the common person:
- Kinetic (motion)
Nuclear energy is not part of our daily lives in Alaska.
The six forms of energy can be converted, one to another. Some
of the conversions are quite simple and common. Others are very
difficult. Electricity converts easily to all of the other forms
of energy. It would be quite difficult to convert sound to other
forms of energy. This subject is addressed mostly in the section