I am sorry for the late reply. I hope the following simulation is what you need.<br />You can drag the arrow to change initial velocity. <p><applet code='users.ntnu.fkh.chargedParticleTowoPlates_pkg.chargedParticleTowoPlatesApplet.class' codebase='ejsuser/2/' archive='ejs_chargedParticleTowoPlates.jar' name='chargedParticleTowoPlates11252' id='chargedParticleTowoPlates11252' width='848' height='359' mayscript=true><param name='draggable' value='true'></applet></p>/htdocs/ntnujava/ejsuser/2/users/ntnu/fkh/chargedParticleTowoPlates_pkg/chargedParticleTowoPlates.properties<a href='htmltag.php?code=users.ntnu.fkh.chargedParticleTowoPlates_pkg.chargedParticleTowoPlatesApplet.class&name=chargedParticleTowoPlates&muid=2' target='_blank'>Full screen applet</a> or <font color="#FF0000">Problem viewing java?</font><a href="http://www.java.com/en/download/help/jcp_security.xml" target="trusted">Add http://www.phy.ntnu.edu.tw/ to exception site list</a><br><b>Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop.</b> This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by/2.5/tw/deed.en">Creative Commons Attribution 2.5 Taiwan License</a><br><a href='ntnujavazip.php?ejsuserjar=11252' title='ejs_chargedParticleTowoPlates.jar' target='userjar'>Download EJS jar file</a>(1200.4kB):double click downloaded file to run it. (19 times by 16 users) , <a href='ntnujavazip.php?ejsuserjar=11252&type=ejs' target='userjar'>Download EJS source</a> <a href='/demolab/phpBB/ejswui.php?ejsuser=ejsuser/2/users/ntnu/fkh/chargedParticleTowoPlates.ejs' target='ejsxml'>View EJS source</a><img src='images/help.gif' onClick='showejsmsg(11252)'><img src='images/plus.gif' onClick='ejsparser(11252,"chargedParticleTowoPlates");'><div id='ejsmsg11252'></div>