Force of Gravity and Circular Motion

Circular Motion Video 1

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Circular Motion Video 2

To get the video in other formats, click here.

Force of Gravity

  • The force of gravity is a force of attraction between any two masses.
  • Gravity gets stronger with greater mass, and weaker with greater distance. The equation for this is:

  • Make sure you can answer questions such as: If the distance between two masses doubles, what will happen to the force of gravity between them?  (Answer: since distance is squared on the bottom, the force will be 1/4 as large.)

Circular Motion

For an object traveling in uniform circular motion:

  • The force and the acceleration are centripetal (pointing towards the center) , and the velocity is tangent to the curve.
  • The acceleration is found by using the equation a = v2/r.
  • Fnet = ma can be replaced by Fnet = mv2/r.
  • For a car on a circular track, Fnet = ma becomes Ff = mv2/r.
  • For orbits, Fnet = ma becomes Fg = mv2/r.

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