Almost every planet has a different gravitational pull (gravitational force). The question is how do we find this force if it isn't given to us and we cannot measure it?

With just the mass and the radius of any planet and your mass, we can find the gravitational force and acceleration on and near the planet’s surface! How about that?

How to find a planet's gravitational force acting on you and the gravitational acceleration...

  1. Choose the planet of interest.
  2. Find the mass and radius in metric units, such as kilograms, meters, etc. (radius = 1/2 of the diameter) of the planet.
  3. You will have to convert kilometers, km, (for the diameter) to meters by multiplying the number of kilometers by 1000.
  4. Write down the gravitational constant, G, for later use (6.673 x 10-11 Nm2/kg2)
  5. Use the equation below where...
    G = the gravitational constant
    M = the mass of the planet
    m = is your mass
    r = the radius of the planet
    Fg = the gravitational force
    gp = gravitational acceleration of planet

  • Plug in the values for G, M, m, and r in the equation and solve.
  • Check and see if your answer comes close to the gravitational acceleration in the table of values for that planet.

Click here for a sample problem!

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