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Physical Science
Physical Science is the study of matter, energy, space and time.
This field of science includes astronomy, atmospheric sciences, chemistry, geology, physics, and oceanography. However, the two main branches of physical science are chemistry and physics. Chemistry involves the study of what substances are made of and how these substances change and combine. Physics is the study of the forms of energy. Energy and the laws of motion are the most basic of the physical sciences and its principles are the basis of all other fields of science.
Questions??
Recently, I was asked some physics questions by a visitor to this site. Since these questions were quite interesting and in depth, I consulted with two physics teachers (Eau Gallie High School & Viera High School) and have posted their detailed answers at the bottom of this page. See bookmark below.
Physics Symbols
The Five Most Important Concepts in Physics
I. Energy
will dissipate from an area of higher energy
to one of lower energy without the input of additional energy.
This law governs all energy flow, especially observable in the cases of thermal and electrical energy flow. Heat moves from the hot coffee to the relatively cold mug and surrounding air. Electrons tend to spread until an even charge is obtained throughout the entire system. This can also be directly observed with a drop of dye added to a glass of water. The color will dissipate until the entire solution is a uniform color.
1st Law: A body in rest tends to stay at rest, and a body in motion tends to stay in motion, unless the body is compelled to change its state. The evidence supporting the first part of this statement is easily seen. We know that a wheel will not begin rolling by itself. However, we do not see the proof of the second half in our world. That is because there is an ever present inhibiting force known as friction that acts as the external force resisting perpetual motion.
2nd Law: The second law is a formula--- Fnet = ma or A=F/m. The product of the object's mass (m) times its acceleration (a), is equal to the net force (Fnet) . Acceleration and force are vectors; in this law the direction of the force vector is the same as the direction of the acceleration vector. The acceleration of a body is dependent upon both the mass of the object (not its weight) and the net force perpetuating the motion (total force in the direction of the motion minus the force resisting motion). In the formula, a resisting force would be written as negative to produce a negative acceleration, which means the object would be slowing down.
3rd Law: For every action there is an equal and opposite reaction. This means that if I push you, I will be slightly pushed back in the process. This is the principle at work behind how jet planes and rockets propel themselves. They expel gases in the opposite direction, are pushed themselves in the process, and therefore move forward.
Motion, or a change in motion, occurs when
a force is applied to an object. Motion has two components, speed and direction.
A change in motion may mean a change in an object's speed, direction, or
both. An object is said to be in motion only if it is changing its position
with respect to a point of reference whose position is fixed.
Newton's Laws
This is where kinematics
comes into play. Kinematics is the science of describing the motion of
objects using words, diagrams, numbers, graphs, and equations. One dimensional
means in motion in a straight line. Therefore, when we talk about one
dimensional kinematics, we will use graphs on a x-axis. Motion can be
forward or backward.
These laws are intimately intertwined and
state that, under normal conditions, the total energy of a contained system
and the total mass of that contained system will remain constant. It also
postulates that neither mass nor energy can be created or destroyed, that
they merely change form (e.g. energy--- electrical changes to thermal,
or mass--- liquid changes to gas). Fairly recently, though under laboratory
conditions, scientists have actually observed a minute loss of total mass
in a closed system, and this has been attributed to the fact that the mass
had actually changed into energy. This led to a modification of the law,
which made the provision that mass and energy can actually change into
each other.
IV. Wave-Particle Duality
The principle of quantum mechanics which
implies that light (and, indeed, all other subatomic particles) sometimes
act like a wave, and sometimes act like a particle, depending on the experiment
you are performing. For instance, low frequency electromagnetic radiation
tends to act more like a wave than a particle; high frequency electromagnetic
radiation tends to act more like a particle than a wave.
V. The Four Fundamental Forces of Nature
Strong- This force is a nuclear force. Its purpose is to hold the nucleus of an atom together, but it decays rapidly with distance; it doesn't even extend beyond an atom's nucleus!!
Weak- The weak nuclear force is associated with beta decay. It is responsible for the nuclear breakdown of neutrons into protons and electrons.
Gravitational- The weakest of the four forces, but still holds us to the Earth, keeps our planet in orbit around the sun, and causes the tides to rise and fall.
Electromagnetic-This force is used on the atomic level to hold the atom together. It is caused by the opposing charges of electrons and protons.
Simple Machines
Compound machines have two or more simple machines working together to make work easier.
In science, work is defined as a force acting on an object to move it across a distance. Pushing, pulling, and lifting are common forms of work. Furniture movers do work when they move boxes. They use a ramp (inclined plane) to slide boxes into their truck. Gardeners do work when they pull weeds. They use a hand shovel (wedge) to help break through the ground and weeds. Children do work when they go up and down on a see-saw (lever). Machines make their work easier. The ramp, the shovel, and the see-saw are simple machines.
Inclined Plane
A slanting surface connecting a lower
level to a higher level
Things move up or down it
Examples: Slide, stairs, ramp, escalator,
slope
A plane is a flat surface. For example, a smooth board is a plane. Now, if the plane is lying flat on the ground, it isn't likely to help you do work. However, when that plane is inclined, or slanted, it can help you move objects across distances. A common inclined plane is a ramp. Lifting a heavy box onto a loading dock is much easier if you slide the box up a ramp--a simple machine.
Wedge
An object with at least one slanting side
ending in a sharp edge
Cuts or spreads an object apart
Examples: Knife, pin, nail, chisel, ax,
snowplow, front of a boat
Instead of using the smooth side of the inclined plane, you can also use the pointed edges to do other kinds of work. For example, you can use the edge to push things apart. Then, the inclined plane is a wedge. So, a wedge is actually a kind of inclined plane. An axe-blade is a wedge. Think of the edge of the blade. It's the edge of a smooth slanted surface. That's a wedge!
Screw
An inclined plane wrapped around a pole
Holds things together or lifts
Examples: Screw, jar lid, vise, bolt,
drill, corkscrew
Now, take an inclined plane and wrap it around a cylinder. Its sharp edge becomes another simple tool: the screw. Put a metal screw beside a ramp and it's kind of hard to see the similarities, but the screw is actually just another kind of inclined plane. Try this demonstration to help you visualize. How does the screw help you do work? Every turn of a metal screw helps you move a piece of metal through a wooden space. And, that's how we build things!
Lever
A stiff bar that rests on a support
called a fulcrum
Lifts or moves loads
Examples: Shovel, nutcracker, seesaw,
crowbar, elbow, tweezers, bottle
opener
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Any tool that pries something loose is a lever. A lever is an arm that "pivots" (or turns) against a "fulcrum" (or point). Think of the claw end of a hammer that you use to pry nails loose. It's a lever. It's a curved arm that rests against a point on a surface. As you rotate the curved arm, it pries the nail loose from the surface.
Wheel and Axle
A wheel with a rod, called and axel, through
its center: both parts move together
Lifts or moves loads
Examples: Car, wagon, doorknob, pencil
sharpener, bike
The rotation of the lever against a point pries objects loose. That rotation motion can also do other kinds of work. Another kind of lever, the wheel and axle, moves objects across distances. The wheel, the round end, turns the axle, the cylindrical post, causing movement. On a wagon, for example, the bucket rests on top of the axle. As the wheel rotates the axle, the wagon moves. On a truck, for example, the cargo hold rests on top of several axles. As the wheels rotate the axles, the truck moves.
Pulley
A grooved wheel with a rope or cable around
it
Moves things up, down, or across
Examples: Curtain rod, tow truck,
mini-blind, flag pole, crane
Instead of an axle, the wheel could also rotate a rope or cord. This variation of the wheel and axle is the pulley. In a pulley, a cord wraps around a wheel. As the wheel rotates, the cord moves in either direction. Now, attach a hook to the cord, and you can use the wheel's rotation to raise and lower objects. On a flagpole, for example, a rope is attached to a pulley. On the rope, there are usually two hooks. The cord rotates around the pulley and lowers the hooks where you can attach the flag. Then, rotate the cord and the flag raises high on the pole.
If two or more simple machines work together as one, they form a compound machine. Most of the machines we use today are compound machines, created by combining several simple machines.
If you've ever tried pulling a stubborn weed or root out of the ground, or tried lifting an engine out of your car, you'll appreciate the invention of levers and simple machines. Using just your bare hands might prove to be difficult or even impossible depending on the task. A tool like a hand shovel or, in the case of the car engine, a pulley fixed to a large tree or beam, makes the seemingly impossible job simple.
| Elements of Machines |
Machines * |
MATTER:
One of the first explanations of the structure
of matter was proposed by the ancient Greeks around 600 B.C. These
philosopher-scholars combined math, logic and their great curiosities to
explain their observations of nature. The early Greeks thought that all
substances were composed of four elements: earth, air, fire, and water.
The term "atom" was later used by the Greeks to describe the smallest part
of an element which still has the properties of that element (More than
20 centuries passed before science was able to prove the existence of the
atom).
Magnetism
is a property of matter in which there is an attraction due to unlike poles.
Magnetism is a force of attraction or repulsion. Magnets have a north and
a south pole, which, if the magnets are allowed to swing freely, point
north and south respectively. Like poles repel and unlike poles attract.
The region in which such magnetic forces can act is called a magnetic field.
Magnetized materials may be either temporary or permanent magnets, depending
on whether they readily lose their magnetic properties.
ENERGY:
Years ago scientists found when work
was being done on a substance heat was produced. It was found that heat
could be transferred from one substance to another. Heat was considered
to be a form of energy and is caused by the movement of molecules within
a substance. This energy of motion is called kinetic energy. Temperature
is related to heat, but heat is not the same as temperature. Heat is a
form of energy. Temperature is a measure of the average kinetic energy
of the molecules in a substance.
Most of the energy you use every day comes from fossil fuels. The three main fossil fuels are coal, oil, and natural gas. Coal is a solid fossil fuel. Fossil fuels are in limited supply and alternative energy resources are being developed to replace them. The sun is an important energy resource. Solar energy can be used in solar heating systems, solar cells, or in wind and water power.
Nuclear energy is released by the splitting of the nucleus of an atom. Energy is released during nuclear fission and nuclear fusion. Fission is the splitting of an atomic nucleus into two smaller nuclei, and fusion is the joining of two atomic nuclei into a single larger nucleus. The energy produced during nuclear fission is mostly heat energy. This heat energy is used to convert water into steam. Electricity is produced from the energy locked within the nucleus of an atom. Nuclear fusion produces more energy than nuclear fission.
Potential
Kinetic
Mechanical
Power
LIGHT
Light
is a form of energy. All types of light
have certain properties in common. The atom is the source of all forms of light,
whether visible or invisible. Light travels at the speed of 300,000,000 meters
per second in a vacuum. A beam of light, starting in the atoms of the sun, will
reach the earth in eight minutes. All light waves are transverse waves.
electromagnetic energy (electromagnetic radiation) is energy that moves through space or a material as a wave. Electromagnetic energy includes light, radio waves, infrared radiation, and x-rays. Electromagnetic energy travels at the speed of light, or 300,000 kilometers per second (186,000 miles per second).
Speed of Light in Vacuum: 3x10x8 m/s, 186,000
miles/sec
Speed of Light in Water: 2.25x10x8 m/s, 140,000 miles/sec
Speed of Light in Diamond: 1.24x10x8 m/s, 77,000 miles/sec
Frequency is the property of a wave that describes how many wave patterns or cycles pass by in a period of time. Frequency is often measured in Hertz (Hz), where a wave with a frequency of 1 Hz will pass by at 1 cycle per second.
White light is the combination of red, blue and green light. As seen in the image above, adding different combinations of light, like red and blue to make magenta, will display varied frequencies of the light spectrum.
Plants respond differently to frequencies (or colors) of light. This is why we use a plant grow light in the classroom terrarium.
What about focal length of light?
Light can be reflected, refracted, and separated into color.
| Light passing through a
convex lens bends toward the center
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Light passing through a concave lens bends away from the center, or appears to spread out
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Astronomers use refracting telescopes (above) to get images like the one
my husband captured of M42 (below)
Stellar Nebula: M42 by Chaz King
This shot taken in Melbourne, FL March 2007
66 minutes of exposure taken over 2 nights
| Hubble Telescope Tracker | |
| Kids Astronomy | |
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| Starchild | |
| Starry Night | |
| DigitaLunatic | Types of Scopes |
| First Scope | Using Scopes |
SOUND
Sound is a form of energy that causes molecules
of a medium to vibrate back and forth. The molecules of the medium vibrate
back and forth in a series of compressions and refractions. Such a disturbance
is best transmitted through elastic materials because the molecules must
return to their original positions after the disturbance has passed. Therefore,
solids are better mediums for sound waves than liquids or gasses. If there
are no molecules of a medium present, there will be no sound.
WEIGHT AND MASS
Weight is a force, it is the pull of Earth's
gravity on an object. While weight of an object is a force, the mass measures
inertia. An object's weight changes if the pull of gravity changes, but
an object's mass is the same everywhere in the universe. If air resistance
were not a factor, everything near the Earth's surface falls with acceleration
g, so weight = mg.
Scientists in History
by Eric Weisstein
| Einstein | Inventions |
| Einstein's Theory Tested | |
| Free Patents Online | Scientific Biography |
All measurements in Science need to be METRIC
Building Structures
Anatomy Building of Collapse
Design and build a bridge that can withstand an earthquake
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Question & Answer:
Recently, I was asked some physics questions by a visitor to this site. I have consulted with two physics teachers, John Carr and Leonard Grasso, and here are their detailed answers:
This section by Leonard Grasso
First of all, the distinction has to be made between contact forces and fundamental forces. Contact forces result from some sort of physical contact between objects. For example, an offensive guard pushing a defensive lineman in a football game, someone pulling on a rope in a game of tug of war, or two cars colliding in an accident.
In contrast, there are four fundamental forces, all of which are associated with fields. They are as follows: gravitational forces, electromagnetic forces, strong nuclear forces, and weak nuclear forces.
All material objects have a gravitational field around them. Material objects actually cause the space around them to bend, and this bending or warping of space is intimately related to an objects gravitational field. It is important not to think of (outer) space as absolute nothingness. It does have properties, one of which is bending in the presence of mass. Einstein's theory of general relativity describes how. The warping of space, or gravity well, around our sun is quite large, whereas the ripple that results from a pencil is extremely small. The Earth also warps space. Since we exist within the space that is being affected by the Earth's mass, we don't notice the effect with our eyes (just like a two dimensional creature trapped within the surface of an inflated balloon would not be aware of the balloon's curvature), but we certainly feel the effect of the Earth's gravitational field interacting with the one that our bodies cause. From a field theory point of view, the gravitational force that we experience on the Earth's surface (or anywhere near the Earth) can be viewed as the result of field interaction (the Earth's gravitational field interacting with our own).
Newton's law of universal gravitation describes the force that two masses exert on each other when separated by a certain distance. Newton's law does not describe how the force is transmitted. The problem of "force acting at a distance" was a problem for Newton and his peers. Einstein offered a whole new perspective on gravitation and how mass affects the space around it. Field theory has served to demystify the problem of how fundamental forces act at a distance to a point, but exactly how fields interact to produce forces is still an exciting area of research in theoretical physics that probably offers more questions than answers.
Moving along, electric charges have electric fields around them, and magnets (or moving charges) have magnetic fields around them. Because electricity and magnetism are intimately related, electric and magnetic forces are grouped together as electromagnetic forces. In contrast to gravitational fields, electric and magnetic fields permeate the space around them (no bending or warping occurs), whereas mass directly affects the space around it. Electric forces result when electric fields interact, and magnetic forces result when magnetic fields interact.
My knowledge of the strong and weak nuclear forces is extremely limited. I know that the strong nuclear force makes possible atomic structure as we know it. Have you ever thought about how it is possible to have an atomic nucleus stay together when it is made up of positively and neutrally charged particles? Positively charged protons should exert repulsive forces on each other and be forced apart, but they are not. The strong nuclear force is the reason why. This force exerts it's effects on subatomic particles at very small distances. If, for example, two protons are brought close enough together with enough energy, the electric force of repulsion that would normally drive them apart can be overpowered by the strong nuclear force which can cause them to be bound tightly together. Conversely, when atoms are "split" as a result of nuclear reactions, it is the energy that has been bound as a result of the strong nuclear force that is released. This energy can be used to power nuclear plants, or can be unleashed through a nuclear weapon.
I also want to point out that the contact forces mentioned previously can be traced back to the electromagnetic force, which ultimately makes collisions and contact possible. Why can't we walk through walls, or why does your body sustain damage when hit? If you try to walk through a wall, electrons in the outer shells of the molecules that make up your body will be repelled by the electrons found in the outer shells of molecules that make up the wall. Ultimately, it's this repulsive (electromagnetic) force that won't allow you to walk through the wall and which makes all physical contact possible.
I think the answers to most of the posed questions can be found in the above explanations. I've shared almost all that I know on the topic, and I am afraid that although some questions are answered, more questions end up presenting themselves. In conclusion, I'll provide some short answer responses to some of the questions that I highlighted.
Q: How does Newton's force of attraction work?
A: One usually does not speak of "Newton's force of attraction" stated as such. There is Newton's universal law of gravitation (mentioned above), and there is Newton's second law of motion (F=ma) which relates force to mass and acceleration.
Q: Are the forces of attraction of gravity and electromagnetism analogous?
A: The forces of gravity and electromagnetism are two of the four fundamental forces found in nature. Modern field theory suggests that those forces result from the interaction of like fields. That is, a gravitational force results when gravitational fields interact, electric forces result when electric fields interact, and magnetic forces result when magnetic fields interact. Note: Gravitational forces can only be attractive, while electric and magnetic forces can be both attractive and repulsive.
Q: Hydrogen attracts oxygen but it doesn't reach over and pick up oxygen and physically move it towards itself like a mother picking up her baby and taking it to her breast (how does this work)?
A: Here, the difference between fundamental forces in nature and contact forces (see above) present themselves. The electromagnetic force is responsible for the attraction and bonding of hydrogen and oxygen atoms. The attraction and bonding occurs through field interaction. On the other hand, a mother picks up her child through physical contact. Physical contact is made, the mother exerts a force on the child, and the child moves.
AP Physics & Physics Honors
Eau Gallie High School
This section answered by John Carr
Q. How does Newton's force of attraction work? Does it work on or in the mass itself?
A. There are forces in the universe that attract. Magnetic, nuclear and gravitational force (the latter being the weakest).
There are still unknowns in the
universe. We know that "gravity" forces, the name for the attraction between
two masses reacts in certain ways. We know that the larger the masses, the
greater the gravitational force. We know that this force decreases by the square
of the distance between them. (i.e.. if you move twice the distance from another
mass, the gravitational force is reduced by a factor of 4). Sometimes in
physics, we only know "what" is happening but not "why". We still have lots to
learn. What physics does is observe actions and try to make relationships of
these observed reactions (formulas).
Q. It works somehow on already moving bodies and is not the cause of these
already moving bodies' motion.
A. Newton's laws state that objects will keep doing what they are doing SO LONG as there are no outside forces acting on the object. Gravity is considered a "force at a distance" like magnetic force and affects mass according to its influence combinations of how much mass and how great a distance it is from the object. A ball is thrown up in the air and slows down because it is being affected by the gravitational force of the earth at a distance from its center mass (radius of the earth). Eventually the ball stops momentarily and starts to speed up because of this same force. (always toward the earth center mass)
IF there is no external forces (a
push or a pull by any forces) then an object will keep doing what it is doing.
In theoretical deep space, an object is not affected by any significant force
and will keep doing what it is doing. If it is moving at a speed, it will keep
moving at that speed for ever. IF it accelerates (speeds up, slows down or
changes direction) it must be affected by an outside force.
Q. You mention that electromagnetism is a force of attraction. Are the forces
of attraction of gravity and electromagnetism analogous?
A. Gravity is generated
by two masses, an electromagnet generates a force by creating
a polarized electric field around a metallic object causing the object to act
like a magnet. Once the flow of electrons thru the coiled wire stops, so does
the polarization.
Q. If the force of attraction
really pulls in gravity, what precisely does one mean by pull?
A. Gravity is
not a force, it is a value of acceleration due to the mass of an object and the
distance from the objects center mass. A gravitational force is generated by
two masses. Kind of like a tree in the woods problem, if there are not two
masses that have gravitational fields, then there is no gravitational force
pulling on them. You can think of gravitational force analogues to a magnetic
force without the repulsion. Masses can only attract each other.
AP Physics & Physics Honors
Viera High School
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