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2012-12-15 13:03:28

Physics: Circular Motion and Gravitation
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  1. Circular motion:
    • motion with constant radius of curvature caused by acceleration being  to velocity.
    • A body moving in uniform circular motion has a constant speed and is accelerated toward the center of the circle.
  2. Tangential speed
    is the speed of an object in circular motion. (the v in the following formula)
  3. Centripetal acceleration:
    acceleration toward center of circular motion;  ac = v2/r
  4. Period:
    time needed to repeat one complete cycle of motion (T).
  5. Centripetal force:
    force that causes centripetal acceleration
    • is also toward the center.
    • is necessary for circular motion.
  6. Newton’s Law of Universal Gravitation:
    • Gravitational force is the mutual force of attraction between particles of matter.
    • Orbiting objects are in free fall.
  7. F between 2 bodies depends on
    • 1. product of their masses
    • 2. divided by the square of the distance between them
    • F α 
  8. Newton’s law of gravitation accounts for?
    • ocean tides.
    • Gravity is a field force.
    • Gravitation field strength equals free-fall acceleration.
    • Weight changes with location.
  9. Kepler’s laws of planetary motion:
    • 1. planets move in elliptical orbits
    • 2. planets sweep out equal areas in equal times
    • Both the period and speed of an object that is in a circular orbit around another object depend on two quantities: the mass of the central object and the distance between the centers of the objects.
  10. Torque and Simple Machines
    • If you want to make an object move, apply a force.
    • If you want to make an object rotate, apply a torque.
  11. Torque
    • is a quantity that measures the ability of a force to rotate an object around some axis.
    • Torque = product of force and the lever arm.
    •  Γ = Fdsinθ
  12. Lever arm:
    distance from axis of rotation to a line along which the force acts.
  13. A machine eases the load either by changing the magnitude or the direction of the force exerted to do work but does not change the amount of work done.  A machine provides a mechanical advantage.
  14. 6 simple machines:
    lever, pulley, wheel & axle (gears = wheel & axle), inclined plane, screw, wedge.
  15. Compound machine is two or more simple machines linked so that Fr of one machine becomes the Fe of the second; AMA of a compound machine is the product of the AMA’s of the simple machines it is made up of.