This applet show normal force/friction force/net force for a ski case.
You can change angle of the slope,friction coeffieient mu, weight.
The Normal force, friction force and net force will be calculated and displayed.
If the Net force is not zero, you can click play (right triangle) to let go.
You can change the scale,too. But All the arrows and text messages will not be displayed.

For the following conditions: mass m (weight=m*g), angle ?. static friction coefficient ?
The normal force N= m*g*cos?.
The component alone the slope =m*g*sin?.
The maximum static friction force Frmax=?*N=?* m*g *cos?.
If m*g*sin? is smaller than ?* m*g *cos? (?>tan?), then the static friction = -*m*g*sin?
If m*g*sin? is larger than  ?* m*g *cos? (?(u[sub]k[/sub] is the coefficient of kinetic friction , which is a little smaller than coefficient of static friction ?)

The following are suggestions from received email message:
[quote]
1.       The friction mu should have 0.1 as default (more realistic for snow) – it is approximately 0.05 at zero degrees Celsius, 0.2 at minus ten degrees
2.       Default slope inclination: 20 degrees
3.       Show two gravity components, one in the opposite direction of the normal force, one along the slope
4.       Show a speed reading (km/h) when the animation starts
5.       The “Drag me” text is not necessary (can be explained elsewhere)
6.       The ability to translate the apple by means of tags.
[/quote]
The applet has been modified according to the above suggestions.
This applet is developed with EJS. You can download the jar file. Download click to run it.
Right click inside the simulation window and select [b]GUI options ->translate[/b] , and select your language from the selection list. Then , translate all the strings, save the result.
Right  click -> GUI options -> language -> your language : to show it.
It should work later on when you run it at your computer.
You will find users/ntnu/fkh/ski_pkg/ski_xx.properties file, where xx the language code.
Please upload property file as attachment so that I can inclide it in the jar file.

Drag force due to air is included. F=(1/2) rho *Cd *Ap *V[sup]2[/sup], where rho=1.2 kg/m[sup]3[/sup],
You can change Cd*Ap with slider.
Cd*Ap=0.11 for an upright body, minimum frontal area
Cd*Ap=0.84 for a horizontal body,maximum frontal area
C*A=0.46 for a body in tuck position

/htdocs/ntnujava/ejsuser/2/users/ntnu/fkh/ski_pkg/ski.propertiesFull screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
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
Download EJS jar file(1351kB):double click downloaded file to run it. (40 times by 29 users) , Download EJS source (24 times by 10 users) View EJS source