# Free Fall

5

Free Fall models a ball that is dropped near the surface of Earth. Newton's second law states that a force F produces an acceleration a that is proportional to the mass m of the falling object.

F = ma .

A freely falling object is acted on by a constant downward gravitational force if we ignore air resistance. Because this gravitational force F is constant and because it is proportional to the mass of the falling object, all objects near Earth fall with the same constant downward acceleration g = 9.8 m/s2. In the Free Fall model, the ball's speed is reduced by a constant factor at every floor collision. All motion takes place in the vertical (y) direction to keep this first Ejs example as simple as possible.

## References:

The Free Fall model is a designed to teach Ejs modeling. Right click within the simulation to examine this model in the Ejs modeling and authoring tool. See:

- "Modeling Physics with Easy Java Simulations" by Wolfgang Christian and Francisco Esquembre, The Physics Teacher, November 2007, 45 (8), pp. 475-480.

The Easy Java Simulations (EJS) manual can be downloaded from the ComPADRE Open Source Physics collection and from the Ejs website.

### Note:

This simulation was created by Wolfgang Christian using the Easy Java Simulations (Ejs) modeling tool. You can examine and modify this simulation if you have Ejs installed by right-clicking within a plot and selecting "Open Ejs Model" from the pop-up menu.

Information about Ejs is available at: <http://www.um.es/fem/Ejs/>.