Transcript Dynamics: The Why of Motion

Dynamics: The Why of
Motion
Inertia, Force, and Newton’s Laws
Inertia
 The property of an object to persist in
its current state of rest or uniform
motion.
 Generally refer to frames of reference
fixed on the earth (since earth
rotates, technically the frame is
accelerating)
 Two frames of reference- inertial and
non inertial (or accelerating)
Forces
 Any kind of push or pull e.g. pushing
on a stroller, pulling on a rope,
kicking a ball, etc
 Forces can act on an object and the
result can be no net motion.
 An object either at rest or travelling
at constant velocity is in equilibrium
Forces
 Can be contact where there is
physical contact between two objects
e.g. shooting a basketball, pulling on
the handle of a wagon
 Can be action-at a-distance forces
which do not have physical contact
e.g. the earth pulls on the moon,
electrical charges attract or repel,
magnets attract or repel
Forces: 4 Fundamental Types




Strong Nuclear
Weak Nuclear
Electromagnetic
Gravitational
Newton’s First Law: Law of Inertia
 An object at rest will remain at rest
and an object in motion will continue
in motion with a constant velocity
(i.e. in a straight line) unless it
experiences a net external force
Newton’s Second Law: Law of
Acceleration
 The acceleration of an object is
directly proportional to the resultant
force acting on it (in the same
direction) and is inversely
proportional to the mass of the object
Newton’s Third Law: Law of
Interaction
 If two objects interact, then the force
on object 1 by object 2 is equal and
opposite to the force exerted on
object 2 by object 1
 F1 2 = - F 2 1