Forces & Motion Laws

  1. normal force
    the "push" force from a surface onto a body in contact with that surface, perpendicular to the surface
  2. weight force
    force exerted by gravitational field in a mass, has downward direction, perpendicular to the surface of the earth
  3. weight equation
  4. gravitational force
    attractive force between two bodies having mass
  5. tension force
    a pulling force on a body usually via an attached cord, rope, cable, or such object
  6. kinetic friction
    resistive force that opposes the relative motion of 2 contacting surfaces that are moving past one another
  7. comparison of kinetic and static friction
    • force required to cause a stationary object to begin moving is usually greater than the force necessary to keep it moving at constant speed
    • kinetic friction < static friction
  8. relationship between object weight and kinetic friction
    kinetic friction will be greater when you try to move a heavy object
  9. relationship between applied force and static friction
    directly proportional; as applied force increases, static friction also increases, and same with decreasing
  10. Fs,max
    greatest applied force without the object moving, due to static friction
  11. static friction
    • resistive force that opposes the relative motion of 2 contacting surfaces that are at rest, with respect to one another
    • measure of how rough or slippery something is; the force needed to get an object moving from a state of rest 
    • its magnitude depends on the amount of microscopic contact points between the surfaces
  12. relationship between friction forces and normal forces
    • frictional forces are proportional to the magnitude of the normal force
    • if something is tilted, there is less normal force and less friction force
  13. Newton's third law
    if two objects interact, the force exerted before object 1 on object 2 is equal in magnitude and opposite in direction to the force exerted by object 2 on object 1
  14. Newton's second law
    the acceleration of an object is directly proportional to the net force acting on it or inversely proportional to its mass
  15. Newton's first law
    an object at rest will remain at rest, and an object in motion at a constant velocity will remain in motion, unless otherwise acted upon by a net external force; law of inertia
  16. mass
    measure of how difficult it is to change an object's velocity
  17. inertia
    tendency of a mass to maintain its state of motion
  18. net external force
    • acts on an object as a result of an interaction between an object and its acceleration
    • sum of all external forces as velocity vectors
    • equivalent to the one force that would produce the same effect as all external forces combined
  19. static equilibrium
    an object is at rest
  20. translational equilibrium
    object moves at straight line with constant velocity
  21. inertial reference frame
    any place where Newton's laws can be applied (all except complex situations)
  22. action-reaction pairs
    • force exerted when two systems interact, both systems "feel" the force in equal but opposite directions
    • never act on the same object (normal and gravity are not a pair), but can interact without touching
  23. force
    the agent (or cause) of an acceleration, change in an object's velocity
  24. contact forces
    • result from physical contact between objects
    • push, pull, friction, normal
  25. field forces
    • no contact between objects
    • gravitational, electric, nuclear, weight, magnetic
  26. fundamental forces
    gravitational, electric, nuclear
  27. free body diagrams
    isolated only the forces affecting the motion of an object, assumed to be acting through a single point; leaves out forces within the object
  28. normal force equation with regards to angle btwn normal force and a vertical line
  29. μk and μs
    • coefficient of kinetic and static friction; ratio of forces of fricton to normal force acting between two objects
    • low with low friction and high with high friction
  30. relationship between mass and acceleration
    • greater mass of an object, less it accelerates under an applied force
    • lighter objects accelerate much more than heavier objects
  31. equilibrium
    • the state at which there is no change in a body's motion
    • there can be many forces acting on the object, they just all have to balance out 
    • net external force must be 0
  32. SI force unit
    Newton, 1kgm/s2
  33. field
    region of influence
  34. force diagram
    • shows objects involved in a situation and the forces exerted on the object
    • all forces are drawn as if they act on a center point, no matter where the force is applied
    • forces exerted by the object are left out because they don't affect the object's motion
Card Set
Forces & Motion Laws