PhysicsCh4
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What is Newton's first law?
The Law of inertia: an object at rest remains at rest and an object in motion remains in motion unless a force is applied

What is Newton's second law?
 Acceleration of object is directly proportional to the net force acting on it
 ΣF = ma
 Sum of forces = mass x acceleration
 VERY IMPORTANT EQ

What is Newton's third law?
 When one object exerts a force on another the second object ALWAYS exerts a force on the first object that is equal in magnitude, but opposite in direction
 F_{AB} = F_{BA}

What is inertia? Mass? Weight?
 Inertia: resistance to a change in motion
 Inertia = Forces / Mass
 Mass: measure of the inertia of an object
 Weight: F_{g} (the force of gravity) = mg

What is a Newton?
 The unit of force
 kg x m / s^{2}

In a force diagram acting on a pull system with two boxes, what are the forces?
 There is no x motion for either, so the only forces acting are
 F_{g} and T
 Remember that T is the same for both boxes
 Also remember that direction of acceleration determines +/ values! (one side up will be + and the other side down with be +)

For an incline plane with no friction, what is the normal force? Acceleration?
 F_{N} = mg(cosθ)
 a_{x} = gsinθ

Static and kinetic friction info
 Static: opposes force on object and prevents movement. The value can vary based on force applied.
 F_{fs} ≤ μ_{s} x F_{N}
 Kinetic: friction during movement, does not change and is not dependent on speed.
 F_{fk} = μ_{k} x F_{N}
 Note  μ_{k} typically less than μ_{s}
 Note  friction ALWAYS opposes velocity

For an incline plane with friction, what is the normal force? Acceleration?
 F_{N} = mg(cosθ)
 a_{x} = g(sinθ + μ_{k} x cosθ)