PhysicsCh4

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Author:
victimsofadown
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203509
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PhysicsCh4
Updated:
2013-02-26 06:32:56
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PhysicsCh4
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PhysicsCh4
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  1. 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
  2. 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
  3. 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
    • FAB = -FBA
  4. What is inertia? Mass? Weight?
    • Inertia: resistance to a change in motion
    • Inertia = Forces / Mass
    • Mass: measure of the inertia of an object
    • Weight: Fg (the force of gravity) = mg
  5. What is a Newton?
    • The unit of force
    • kg x m / s2
  6. 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
    • Fg 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 +)
  7. For an incline plane with no friction, what is the normal force? Acceleration?
    • FN = mg(cosθ)
    • ax = gsinθ
  8. Static and kinetic friction info
    • Static: opposes force on object and prevents movement.  The value can vary based on force applied.
    • Ffs ≤ μs x FN
    • Kinetic: friction during movement, does not change and is not dependent on speed.
    • Ffk = μk x FN
    • Note - μk typically less than μs
    • Note - friction ALWAYS opposes velocity
  9. For an incline plane with friction, what is the normal force? Acceleration?
    • FN = mg(cosθ)
    • ax = g(sinθ + μk x cosθ)

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