3-Circular Motion & Gravity

Slideshow found here: Circular Motion and Universal Gravity Google Slideshow

Text Book: Chapter 4 in Mastering Physics (get online code for registration on about page of google classroom)


    • Distinguish between & plan experiments to measure gravitational mass and inertial mass.
    • calculate Fg in a gravitational field.
    • calculate gravitational field strength (g) near the surface of an object based on radius and mass relative to the earth (or other reference objects)
    • Calculate gravitational force between 2 objects (include orbits and non-orbital situations)
    • Determine when gravitational forces are the dominant force and other forces can be ignored
    • All force objectives continue to apply

Equations from the formula chart:

Equations you should be able to memorize or come up with on your own:

Video Lessons, including example problems of moderate difficulty.

Common Misconceptions (each of the following statements are incorrect)

  • Circular Motion
    • Circular motion does not require a force.
    • Centrifugal forces are real.
    • An object moving in circle with constant speed has no acceleration.
    • An object moving in a circle will continue in circular motion when released.
    • Misconception: An object is circular motion will fly out radially when released (meaning it will fly out along a line extended out from the center through the point of release).
      • Correct principle: The velocity of an object traveling in a circular path is tangential to the circle (meaning 90 degrees to the line going from the center to the point where the object is), and once released from whatever is holding it in the circular path, the ball will continue in the direction of the velocity. See the animated ball rolling around the pie pan.
  • Gravitation
    • The Moon is not falling.
    • The Moon is not in free fall.
    • The force that acts on apple is not the same as the force that acts on the Moon.
    • The gravitational force is the same on all falling bodies.
    • There are no gravitational forces in space.
    • The gravitational force acting on the Space Shuttle is nearly zero.
    • The gravitational force acts on one mass at a time.
    • Moon stays in orbit because the gravitational force on it is balanced by the centrifugal force acting on it.
    • Weightlessness means there is no gravity.
    • The Earth's spinning motion causes gravity.