Transcript force

FORCES OVERVIEW
KARL PHYSICS
FORCES are
any push or
pull. Forces
accelerate
objects.
GRAVITY
AMERICAN HERITAGE DICTIONARY
Gravity is the fundamental force of attraction that ALL objects with mass
have for each other. Like the electromagnetic force, gravity has effectively
infinite range and obeys the inverse-square law. At the atomic level, where
masses are very small, the force of gravity is negligible, but for objects that
have very large masses such as planets, stars, and galaxies, gravity is a
predominant force, and it plays an important role in theories of the
structure of the universe.
NUCLEAR FORCES
www.ric.edu/faculty/ptiskus/At
omic_Force/
APPLIED forces are forces applied
to one object by another object.
ACTION AT A DISTANCE VS. CONTACT FORCES Action-at-adistance forces are those types of forces that result even when
the two interacting objects are not in physical contact with each
other, yet are able to exert a push or pull despite their physical
separation. Examples of action-at-a-distance forces include
gravitational forces. For example, the sun and planets exert a
gravitational pull on each other despite their large spatial
separation. Even when your feet leave the earth and you are no
longer in physical contact with the earth, there is a gravitational
pull between you and the Earth. Electric forces are action-at-adistance forces. For example, the protons in the nucleus of an atom
and the electrons outside the nucleus experience an electrical pull
towards each other despite their small spatial separation. And
magnetic forces are action-at-a-distance forces. For example, two
magnets can exert a magnetic pull on each other even when
separated by a distance of a few centimeters.
Contact Forces – friction, tension, normal, air resistance,
applied, spring
Action-at-a-Distance Forces – gravity, electrical, magnetic
Force is a quantity that is measured using the standard metric
unit known as the Newton. A Newton is abbreviated by an "N." To
say "10.0 N" means 10.0 Newton of force. One Newton is the
amount of force required to give a 1-kg mass an acceleration of 1
m/s/s.
Physicsclassroom.com
4 FUNDAMENTAL FORCES
As you sit in front of your computer reading this article, you may be unaware
of the many forces acting upon you. A force is defined as a push or pull that
changes an object's state of motion or causes the object to deform. Newton
defined a force as anything that caused an object to accelerate -- F = ma, where
F is force, m is mass and a is acceleration.
The familiar force of gravity pulls you down into your seat, toward the Earth's
center. You feel it as your weight. Why don't you fall through your seat? Well,
another force, electromagnetism, holds the atoms of your seat together,
preventing your atoms from intruding on those of your seat. Electromagnetic
interactions in your computer monitor are also responsible for generating light
that allows you to read the screen.
Gravity and electromagnetism are just two of the four fundamental forces of
nature, specifically two that you can observe every day. What are the other
two, and how do they affect you if you can't see them?
The remaining two forces work at the atomic level, which we never feel,
despite being made of atoms. The strong force holds the nucleus together.
Lastly, the weak force is responsible for radioactive decay, specifically, beta
decay where a neutron within the nucleus changes into a proton and an
electron, which is ejected from the nucleus.
Without these fundamental forces, you and all the other matter in the
universe would fall apart and float away. Craig Freudenrich, Ph.D.
FORCE FIELDS occur for action at a
distance forces – gravity and
electromagnetic
forces
FRICTION
AIR RESISTANCE
INTERNAL VS. EXTERNAL FORCES physicsclassroom.com
Forces can be categorized as internal forces or external forces. There are many sophisticated and
worthy ways of explaining and distinguishing between internal and external forces. Many of these
ways are commonly discussed at great length in physics textbooks - particularly college-level physics
textbooks. For our purposes, we will simply say that external forces include applied force, normal force,
tension force, friction force, and air resistance force. And for our purposes, the internal forces include
the gravity forces, magnetic force, electrical force, and spring force. While this is a simplistic approach,
it is an approach that will serve us well in our introduction to physics.
The importance of categorizing a force as being either internal or external is related to the ability of
that type of force to change an object's total mechanical energy when it does work upon an object. When
net work is done upon an object by an external force, the total mechanical energy (KE + PE) of that
object is changed. If the work is positive work, then the object will gain energy. If the work is negative
work, then the object will lose energy. The gain or loss in energy can be in the form of potential energy,
kinetic energy, or both. Under such circumstances, the work that is done will be equal to the change in
mechanical energy of the object. This principle will be discussed in great detail later in this lesson.
Because external forces are capable of changing the total mechanical energy of an object, they are
sometimes referred to as nonconservative forces.
When the only type of force doing net work upon an object is an internal force (for example,
gravitational and spring forces), the total mechanical energy (KE + PE) of that object remains constant.
In such cases, the object's energy changes form. For example, as an object is "forced" from a high
elevation to a lower elevation by gravity, some of the potential energy of that object is transformed into
kinetic energy. Yet, the sum of the kinetic and potential energies remains constant. This is referred to
as energy conservation and will be discussed in detail later in this lesson. When the only forces doing
work are internal forces, energy changes forms - from kinetic to potential (or vice versa); yet the total
amount of mechanical is conserved. Because internal forces are capable of changing the form of energy
without changing the total amount of mechanical energy, they are sometimes referred to as
conservative forces.
NORMAL OR SUPPORT FORCE
TENSION, ELASTIC AND SPRING FORCES
FORCE VECTORS AND RESULTANTS
BUOYANT
FORCE
NEWTON = THE METRIC UNIT OF FORCE (N)
A force is a push or a pull, or more generally anything
that can change an object’s speed or direction of motion. A
force is required to start a car moving, to slow down a
baseball player sliding in to home base, or to makean
airplane turn. (Forces may fail to change an object’s
motion if they are canceled by other forces, e.g. the force
of gravity pulling you down right now is being canceled by
the force of the chair pushing up on you.) The metric unit
of force is the Newton, defined as the force which, if
applied for one second, will cause a 1-kilogram object
starting from rest to reach a speed of 1 m/s.
ALL FORCES ARE MEASURED IN NEWTONS
www.faqs.org/docs/Newtonian
ELECTROMAGNETIC FORCES
An electromagnetic force is a physics concept that refers to
a particular force, or influence, that affects charged
particles. These particles may be positively or negatively
charged. The force, which is carried via photons, is
responsible for holding electrons and protons together in
an atom, and holding atoms together in a molecule. We
encounter electromagnetic forces daily; they are the
reason behind attraction and repulsion of magnets and
electrical charges, and they factor in chemical reactions as
well.
NET FORCE
BALANCED VS. UNBALANCED FORCES
FORCES CONNECTED TO IMPULSE
Work is a Result of Force
by Ron Kurtus (revised 12 October
2008)
Work is defined as the result of
applying a force to an object in order to
move it a certain distance. In other
words, work equals force times
distance. Work is always against some
resistance.
CENTRIPETAL
FORCE
NEWTONS 1ST LAW
NEWTON’S 2ND LAW
NEWTON’S 3RD LAW