Unit II: Newton’s Laws
Subunit A: Balanced Forces
Ch 4 of Texas Physics p. 118 - 151
Variables, Units
NOTES:
Equations
Newton's first law of motion (AKA "law of
inertia"):
An object at rest will remain at rest, an object
in motion will remain in motion, in a straight
line unless acted upon by an unbalanced
force.
Inertia: the tendency of an object to resist a
change in motion.
Force: an action that may cause a change in
an object's motion. (could be a push or a pull)
Net force: The resultant force vector (the sum
of all forces) acting on an object.
Equilibrium: when the Net force on an object
is zero.
* mass is a measure of inertia
* inertia is directly proportional to mass
* inertia depends only on mass (not on motion)
* more inertia means greater resistance to
change in motion
* change in motion = change in speed and/or
direction = change in velocity = acceleration
* recall the difference between mass and
weight:
- mass is the same everywhere in the
universe (independent of gravitational field)
- weight is directly proportional to mass, but
changes from place to place depending on the
gravitational field strength
more mass = more inertia = harder to push
same
moose has more mass = more inertia =
harder to change directions
newton's 3rd law "action reaction law"
When object A exerts a force on object B,
object B exerts a force on object A that is
equal in magnitude but opposite in direction
Why don't action reaction force pairs cancel
each other out?
--> because they act on 2 DIFFERENT
objects