# 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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 Author: victimsofadown ID: 203509 Filename: PhysicsCh4 Updated: 2013-02-26 11:32:56 Tags: PhysicsCh4 Folders: Description: PhysicsCh4 Show Answers:

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