Rotational Equilibrium & Dynamics

  1. torque
    • a quantity that measures the ability of a force to rotate an object around some axis
    • greater torque means greater ability to rotate an object
  2. lever arm
    the perpendicular distance from the axis of rotation to the line drawn along the direction of the force
  3. center of mass
    the point at which all the mass of the body can be considered to be concentrated when analyzing translational motion
  4. moment of inertia
    the tendency of a body rotating about a fixed axis to resist a change in rotational motion
  5. angular momentum
    the product of a rotating object's moment of inertia and angular speed about the same axis
  6. rotational kinetic energy
    the energy of an object due to its rotational motion
  7. t=flθ
    torque=magnitude of the force x l the distance from the axis of rotation to the force (aka lever arm) x angle btwn force and distance from axis
  8. torque SI units
  9. positive/negative rotation
    • positive: counter clockwise
    • negative: clockwise
  10. what produces torque
    only the tangential component of force produces torque; not the radial force
  11. equilibrium with rotational motion
    • neither linear nor rotational motion will change 
    • all external forces and torques must be zero
  12. translational equilibrium
    sum of net forces is zero; force condition
  13. rotational equilibrium
    sum of net torques must be zero; torque condition
  14. extended object
    object that has a definite, finite size and shape
  15. axis of rotation
    like a line that passes through a hinge that allows things to rotate
  16. relationship btwn lever arm and torque
    • farther the force is from the axis of rotation, the easier it is to rotate an object and the more torque is produced
    • smaller torque=shorter lever arm
  17. center of gravity
    position at which Fg acts on extended object as if it were point mass
  18. moment of inertia
    tendency of a body rotating with a fixed axis to resist a change in rotational motion
  19. difference btwn mass and moment of inertia
    mass is intrinsic, moment of inertia is not
  20. relationship between mass distance from axis and moment of inertia
    farther mass is from axis, greater moment of inertia, greater difficulty to rotate
  21. relationship btwn mass and moment of inertia
    moment of inertia is greater for more massive things
  22. second condition for equilibrium
    complete equilibrium depends on both no net force and no net torque
Card Set
Rotational Equilibrium & Dynamics