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+//(2.6) The rate of heat transfer between a certain electric motor and its surroundings varies with time as Qdot = -.2[1-e^(-.05t)] where t is in seconds and Qdot in KW.The shaft of the motor rotates at a constant speed of omega = 100 rad/s and applies a constant torque of tau = 18 N.m to an external load. The motor draws a constant electric power input equal to 2.0 kW. For the motor, plot Qdot and Wdot,each in kW, and the change in energy deltaE in kJ, as functions of time from t =0 to t = 120s.
+
+//solution
+
+//initializing variables
+omega = 100;                      // motor rotation speed in rad/s
+tau = 18;                         //torque applied by shaft in N.m
+Welecdot = -2;                    // electric power input in KW
+
+funcprot(0);
+Wshaftdot = (tau*omega)/1000;     //shaft work rate in KW
+Wdot = Welecdot + Wshaftdot;      //net work rate in KW
+
+function [Qdot]=f(t)
+    Qdot = (-.2)* [1-%e^(-.05*t)];
+endfunction
+
+function [Edot]=f1(t)              //function for rate of change of energy
+    Edot =(-.2)* [1-%e^(-.05*t)] - Wdot ;
+endfunction;
+
+function [deltaE] =f2(t)           //function for change in energy  
+    deltaE = intg(0,t,f1);    
+endfunction;
+
+t = linspace(0,120,100);
+for i = 1:100
+    Qdt(1,i)= f((120/99)*(i-1));
+    Wdt(1,i)= Wdot;
+    dltaE(1,i)= f2((120/99)*(i-1));
+end
+plot2d(t,Qdt,rect=[0,-.25,120,0]);
+plot2d(t,Wdt,style=5,rect=[0,-.25,120,0]);
+xtitle("","time,s","Qdot,Wdot,KW");
+legend("Qdot","Wdot");
+xset('window',1);
+plot2d(t,dltaE);
+xtitle("deltaE versus time","Time, s","deltaE, KJ");