Free Particle Model Inertia Interaction by gqz18849


									           Free Particle Model: Inertia & Interaction
Key Ideas:

1. Forces (pushes and pulls) are interactions between two objects. Forces between objects
are differentiated by the way in which two objects interact:

 When two surfaces touch each other, forces perpendicular to the surfaces are called
normal forces and forces parallel to the surfaces in contact are frictional. The Friction
force that allows us to step forward or keeps car wheels from spinning can be called
traction. When we touch things a combination of both normal and frictional forces are
present. For simplicity, we can call a combination force a push or a pull.
 Extended or linked materials such as a string or chain exert tension forces on an
 When an object interacts with a fluid, such as water or air, propelling forces are called
thrust, resistive forces are called drag, floating forces are called buoyant, and steering
(or Bernoulli's) forces are called lift.
 When two objects interact without touching, they exert forces through a force field.
Earth, for example, exerts a gravitational force on the Moon even though the Earth and
Moon do not touch. Other non-contact forces include electric and magnetic forces.
When we label forces, we want to indicate the type of interaction between the objects,
what object the force is acting on and what object the force is by. Therefore, we will use
the following notation:

   Fkind of force, on feeler, by dealer (for example: Fgravity, on student, by earth)
2. Newton's First Law, the law of inertia.

Newton's First Law: Objects at rest stay at rest, objects in motion stay in motion at
constant speed in a straight line unless acted upon by unbalanced forces.

      Therefore, objects acted upon by balanced forces will not accelerate -- they
       instead remain at constant velocity.
      "Inertia" refers to an object's "resistance" to change in its constant velocity
       motion. Inertia is not an interaction between objects, and therefore inertia is not a
      The more mass an object has, the more noticeable the property of inertia is. Mass
       is a quantitative measure of an object's inertia.

3. Newton's Third Law, forces are interactions (sometimes called the law of action and

Newton's Third Law: All forces come in pairs; paired forces are equal in magnitude, but
opposite in direction. FAB = -FBA
Another way of thinking about Newton's third law: You can't touch without being
touched and you can only touch as hard as you are touched.

4. Quantitatively, forces are measured in Newtons (pounds in the English system). Mass
is measured in kilograms.

5. Earth's gravitational field strength at its surface is 10 Newtons of force on every
kilogram of mass. The force gravity exerts on an object is called its weight. weight = 10
N/kg * mass

6. When analyzing the forces acting on an object:
    a. draw and label a force diagram for the object
    b. choose the simplest coordinate axis for analysis: horizontal-vertical or parallel-
    c. break forces not aligned with your coordinate axis into components using
    d. qualitatively use marks on the vectors to indicate equality and inequality
    e. write equations for the vector equality marks to quantitatively calculate force values
    f. state whether the velocity of the object is constant (balanced forces) or changing
(unbalanced forces)

Source: Schober’s Physics

To top