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Motion and Stability: Forces and Interactions (PS2) (STABILITY &…
Motion and Stability: Forces and Interactions (PS2)
FORCES & MOTION
Newton's 2nd Law
F=ma (Force = Mass x Acceleration)
Some Exceptions
Large Scale (close to the speed of light)
Changing Mass + Changing Speed (at same time)
Small Scale (molecular, atomic, subatomic)
Second Law
Newton's 3rd Law
Third Law
For every action, there is an opposite and equal reaction
Newton's 1st Law
Objects at rest tend to stay at rest and objects in motion tend to stay in motion.
First Law
TYPES OF INTERACTIONS
Four Fundamental Forces
Strong Nuclear Forces: important inside atomic nuclei
Gravitational Forces
WHEN OBJECTS DON'T TOUCH:
force fields contain energy and transfer energy through space
Tested with mass
always attractive
negligible in small objects, noticeable with huge objects like planets
Long-range gravitational interactions govern the evolution and maintenance of large-scale
structures
in the universe and the patterns of
motion
within them.
Objects with mass are sources of gravitational fields and are affected by the gravitational fields of all other objects with mass
Newton's Law of Universal Gravitation
Law of Universal Gravitation
Mathematical model to describe and predict the effects of gravitational forces between distant objects
Weak Nuclear Forces: important inside atomic nuclei
Electromagnetic Forces
WHEN OBJECTS DON'T TOUCH
force fields that contain energy and transfer energy through space
Tested with charge for electric field and magnet for magnetic field.
WHEN OBJECTS TOUCH
result from deformation of object's substructures
result from electric charges that form those substructures
electric and magnetic forces are different aspects of single electromagnetic interaction
magnitude variance, depending on magnitudes of charges, currents, magnetic strength, & distance between objects
attractive or repulsive, depending on relative sign of electric charges, direction of current flow, & orientation of magnets
All objects with electrical charge or magnetization are sources of electric or magnetic fields and can be affected by the fields of other such objects.
Coulomb's Law
Like charges repel, opposite charges attract
The closer the charges are, the greater that attraction or repulsion will be
mathematical model to describe and predict the effects of electrostatic forces between distant objects
Coulomb's Law
Defined as a
push or a pull
Forces can cause a change in motion of one or more interacting objects. These interactions can be explained and predicted.
Described by
Direction
Strength
(measurable and comparable)
STABILITY & INSTABILITY IN PHYSICAL SYSTEMS
Stable System with Noticeable Changing Cycles (looks unstable)
Regular patterns of change allow for predictions about the systems future
Example: Earth orbiting the sun, system of tides
Stable System
small change results in forces that return the system to its prior state
Example: a punching bag
Stable System with "Unseen" Changing Processes
Flows or processes within the system are going on at opposite but equal rates
Example: a person maintaining a steady weight despite eating, burning calories, sweating, excreting waste.
Static and Unstable System
small change leads to forces that tend to increase that change
Example: a ball at the top of a hill, dominos stacked up in lines
MOMENTUM
p=mv (momentum = mass x velocity
mass = how big something is
velocity = how fast it's going
Total momentum within a system changes only when momentum is transferred into or out of the system
because of external forces acting on the system
because of matter flows
Stability and instability in a given system depend on balance of competing effects
With no energy inputs, an unstable system will continue to change until it reaches stability
Conditions and properties of the objects within a system affect the rates of energy transfer and thus how fast or slowly a process occurs.
Feedback Loop: feedback mechanisms that shift a system back to stability
We may not be able to predict the future of complex system due to a great number of component pieces BUT we can predict average properties and behaviors
