Install Ejs and then right-click on a launch node (green arrow) to copy the Free Fall model from this jar file into the Ejs workspace to do the following activities.

Friction

The Free Fall model assumes that energy is lost only during the floor collision. Set the coefficient of restitution to 1.0 in the model and modify the differential equation to include energy loss due to friction (fluid drag). This energy loss can be modeled by including a friction force Ffriction that is proportional to the velocity:

Ffriction= - b v .

The drag coefficient b depends on the shape of the object and should be included in the model as an additional variable. A good value for simulation is b/m =0.1 although realistic values for objects in air is lower. What is the significance of the negative sign in the friction formula?

**My input/contributions are**

1. variable k

2. variable mass

3. ODE becomes dvy/dt = -g - k/mass*(vy)

1. variable k

2. variable mass

3. ODE becomes dvy/dt = -g - k/mass*(vy)

**source code**

download the *.jar for using the applet on standalone without internet connection.

download the *.jar for using the applet on standalone without internet connection.

**Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop.**This work is licensed under a Creative Commons Attribution 2.5 Taiwan License

- Please feel free to post your ideas about how to use the simulation for better teaching and learning.
- Post questions to be asked to help students to think, to explore.
- Upload worksheets as attached files to share with more users.