I hope the following simulation is what you need.

You can drag those 3 vectors (labeled as 1,2,3), the simulation will calculate the missing force.
Information about missing force will be diaplaced when the answer checkbox is checked.

/htdocs/ntnujava/ejsuser/2/users/ntnu/fkh/missingforce_pkg/missingforce.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(927.3kB):double click downloaded file to run it. (29 times by 16 users) , Download EJS source View EJS source