The Earth and a mass are shown on the screen along with vector representing the force on the object. You can click-drag on the mass to change its position. You can move the mass inside the Earth to the center. You can also change the mass of either the earth or the mass. Find an equation for the force on the mass. You can also select other planets.
ME= mass of Earth and mb= mass of the red ball. d is the distance between the center of the Earth and the center of the ball. Fg is the gravitational force on the ball. The position is in Mm (Mega m, Millions of meters), force is in Newtons, while mass is in kg. Each block on the grid represents 1 Mm in distance or 1 N when measuring force.
When you click run the ball falls through the center of the Earth.
Animation created by John M. Clement © 2004 all rights reserved.