//updated 11/14/00-added complete solution
thepage="Energy, heat and work-word problems(68)"
//11/20/02-updated netscape 7
refnumber=144
//updated 9/7/98 added show answer
//globals
attempts=corrt=totl=tried=0
theanswer=missing=0
given=0
alldata=0
symbols=new Array("δU","q","w")
equations=new Array()
equations[0]=symbols[0]+"="+symbols[1]+"+"+symbols[2]
equations[1]=symbols[1]+"="+symbols[0]+"-"+symbols[2]
equations[2]=symbols[2]+"="+symbols[0]+"-"+symbols[1]
ansphrase=new Array("The total energy change is the sum of the heat and the work.<br>","The heat is the difference between the total energy and the work.<br>","The work is the difference between the total energy and the heat.<br>")
//This function clears all values in both tables on loading the page
//This function clears the first table
question=new Array()
question[0]=new Array("What is the total energy change if a system ")
question[1]=new Array("What is the heat change if a system ")
question[2]=new Array("What is the work if a system ")
//This is the function started when "New Problem" is pushed	
//This function first clears all old values using clear()
//The three variables(mass,moles and gfw) are then determined, using Math.random() to 
//generate gfw and mass and a ratio to generate moles. 
function startit(){
	clear()
	totl++
	document.forms[0].total.value=totl
	alldata=new Array()
	for(var j=0;j<3;j++)alldata[j]=0;	
	while(alldata[1]<50)alldata[1]=Math.round(500*Math.random());	
	if(Math.random()>.5)alldata[1]=-alldata[1];
	while(alldata[2]<50)alldata[2]=Math.round(500*Math.random());
	if(Math.random()>.5)alldata[2]=-alldata[2]
	alldata[0]=Math.round(alldata[1]+alldata[2])
//The three variables are then converted to two significant figures.
	//for(var j=0;j<3;j++)alldata[j]=number(alldata[j],2,3)
	buildquestion()
}
//This function partially fills the table, setting the problem
function buildquestion(){
	missing=Math.floor(3*Math.random())
	thequest=question[missing][0]
	if(missing==0){
		alldata[1]>0?thequest+=" gains ":thequest+=" loses ";
		thequest+=Math.abs(alldata[1])+"<b>J</b> of heat while";
		alldata[2]>0?thequest+=" the surroundings does ":thequest+=" doing ";
		thequest+=Math.abs(alldata[2])+"<b>J</b>";
		alldata[2]>0?thequest+=" on the system?":thequest+=" on the surroundings?";
		
		
	}
	if(missing==1){
		alldata[0]<0?thequest+=" loses a total of ":thequest+=" gains a total of ";
		thequest+=Math.abs(alldata[0])+"<b>J</b> while ";
		alldata[2]>0?thequest+=" the surroundings does ":thequest+=" doing ";
		thequest+=Math.abs(alldata[2])+"<b>J</b> of work";
		alldata[2]>0?thequest+=" on the system?":thequest+=" on the surroundings?";
	}
	if(missing==2){
		alldata[0]<0?thequest+=" loses a total of ":thequest+=" gains a total of ";
		thequest+=Math.abs(alldata[0])+"<b>J</b> while ";
		alldata[1]>0?thequest+=" gaining ":thequest+=" losing ";
		thequest+=Math.abs(alldata[1])+"<b>J</b> of heat" 
	}
	buildanswer()
	showquest(thequest)
}
function buildanswer(){
	getsolved()
	theanswer=ansphrase[missing]+equations[missing]+"<br>"+solved[missing]
}
function getsolved(){
	solved=new Array()
	solved[0]=alldata[1]+"+"+alldata[2]+"="+alldata[0]+"<b>J</b>"
	solved[1]=alldata[0]+"-"+alldata[2]+"="+alldata[1]+"<b>J</b>"
	solved[2]=alldata[0]+"-"+alldata[1]+"="+alldata[2]+"<b>J</b>"
}
// This is the "Check Answer Function
//This function checks for correctness by simply seeing if a/b is within 1%
//of c. The results are then posted to the second table. If you change the
//relationship between a and b, above, make sure you change this also.
function answer(ans){
	if(tried==1)alert("You've done this one. Get a new problem!")
	else{
	if(tried==2){totl++;document.forms[0].total.value=totl}
	attempts++
	if (ans==alldata[missing]){	
		document.forms[0].results.value="correct"
		corrt++
		document.forms[0].correct.value=corrt
		tried=1
	}
	else {
		document.forms[0].results.value="incorrect"
		tried=2
		document.forms[0].elements[missing].select()
		document.forms[0].elements[missing].focus()
	}
	}
}