This applet calculates the gravitational force, gravitational field strength, gravitational potential energy and gravitational potential.

If the applet does not appear, please try the following:
(1) Download the Java software from
(2) Go to the menu: Tools > Turn off Pop-Up Blocker.
(3) Tools > Internet Options > Advanced > Security > Allow Active Contents.
(4) Start Menu > All Programs > Java > Configure Java > Security and then add this website to the Exception Site List.

Exercises for students:
Find the gravitational force experienced by a person of mass 100 kg standing on the surface of the earth, given that the radius of the earth is 6371 km.
Find the gravitational force between the earth and the moon (mass of earth = 5.972E24 kg, mass of moon = 7.348E22 kg, distance between earth and moon = 384,400 km).
Find the gravitational field strength experienced by a geostationary satellite (distance 35,786 km from the surface of the earth).
Find the work done by gravity to move an object of unit mass from infinity to the surface of the earth.

Gravitational force = GMm/r2
Gravitational field strength = GM/r2
Gravitational potential energy = -GMm/r
Gravitational potential = -GM/r

Right-click here to download this page and the Java Class File.