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Core Idea PS2: Motion and Stability: Forces and Interactions (PS2.A:…
Core Idea PS2:
Motion and Stability: Forces and Interactions
PS2.A: Forces and Motion
forces are described by their strength and direction
Static object
multiple forces acting on it
Newton's 3rd Law
force of 1st object on 2nd object is equal in strength to force of 2nd object on the 1st, but in the opposite direction
Newton's 2nd Law
F=ma (total force= mass times acceleration)
PS2.B: Types of Interactions
Gravitational Forces
objects with mass are sources of gravitational fields
always attractice
objects are pulled toward Earth's center
Electromagnetic Forces
attractive or repulsive depending on sign of electric charges
magnitude depends on magnitudes of charges, currents, and magnetic strengths and distances between interacting objects
all objects with electrical charge or magnetization are sources of electric or magnetic friends
strong and week nuclear interactions
important inside atomic nuclei
determine nuclear-sizes, stability, and rates of radioactive decay
PS2.C: Stability and Instability in Physical Systems
Stable System
any small change results in forces that return system to prior state
Static does NOT mean stable
Ex: A ball sitting on top of a hill is static, but unstable
System can be changing but have a stable repeating cycle of changes
Ex: Earth orbiting the sun
Unstable System
Any small change leading to forces that increase the change
dependant on the balance of competing effects
sum of forces is 0