Definitions
for Force: 1)
Force is a push or pull 2)
Force is the capacity to do work or cause physical change 3)
Force= Mass times acceleration (F = ma)
4) A force is that which changes or tends to change the state of rest or motion
of a body. Examples: For
simplicity sake, all forces (interactions) between objects can be placed into
two broad categories: contact forces, and forces resulting from actionatadistance. Contact
Forces include: frictional forces, buoyant forces, normal forces, and air
resistance forces Actionatadistance
forces include: gravitation, electrostatic and magnetic forces. Measuring
Force: Force
is measured using either the English System of Measurements or the International
System of Units (SI). Common
Units of Force >>SI:
Newton (N) 1 N = 0.225 lb; One
Newton (N) of force is defined as the amount of force needed to accelerate 1 kilogram
(kg) of mass at a rate of 1 meter per second squared (m/s2). 1
Newton = 1 kg m/sec2 (A kilogram is the amount of weight at which 1 N of force
will accelerate at a rate of 1 m/s2.) >>English
System: Pound (LB) 1 LB = 4.448 N
In English system of measurements, a slug is the amount of mass that 1 pound of
force will accelerate at 1 ft/s2, and a pound mass is the amount of mass that
1 LB of force will accelerate at 32 feet/s2. Describing
a Force: A
force is a vector
quantity. A vector quantity is a quantity which has both magnitude and direction.
To fully describe the force acting upon an object, you must describe both its
magnitude and direction. Thus, 10 Newtons of force is not a complete description
of the force acting on an object. 10 Newtons, downwards is a complete description
of the force acting upon an object. (Note:
What is the difference between vector
and scalar quantities? A vector has both strength and direction, a scalar
quantity can be described using only 1 quantity, magnitude. Examples of scalar
quantities are: time, energy and volume since they only represent magnitude and
no direction. What
is the Difference between Mass and Weight? Shown
below are two types of scales commonly used in the classroom a spring scale
(left) and a simple balance beam scale on the right. On
earth the spring scale reads 100g with an unknown mass attached at the bottom.
To balance the scale on the right a 100g mass was also needed. If
we were to take both scales to the moon, what would the the spring scale read?
How much mass would be needed to balance the 100g mass on the balance beam? Can
you explain your answer? For more details see the Mass
and Weight Page.

 
spring scale   simple
balance scale  What
does applying a Force do? Force
causes acceleration. Newton's
Second Law states that: the
acceleration (a) of an object is directly proportional to the force (F) applied,
and inversely proportional to the object's mass (m).
That means that the more force you apply to an object, the greater the acceleration.
And, the more mass the object has, the lower the acceleration. Newton's
Second Law can be written in equation form: F = ma. For
falling objects we can write F=mg where g is the acceleration due to gravity.
The force of gravity
is what causes free falling objects to accelerate. These objects all accelerate
at the same rate of 9.8 meters/sec^2 What
is Friction?
Friction
is the force that opposes the relative motion or tendency to such motion of two
bodies in contact. If we try to push a block of wood across a table, there are
two opposing forces
that act: the force associated with the push, and a force that is associated with
the friction which acts in the opposite direction. As
frictional forces are decreased (for example, by placing oil on the table) the
object moves further and further before stopping. This demonstrates Galileo's
law of inertia which states: an
object in a state of motion possesses an ``inertia'' that causes it to remain
in that state of motion unless an external force acts on it. 