//Example 11_2 clc;clear;funcprot(0); //Properties rho_a=1.20;// The density of air in kg/m^3 rho_g=.8;//The density of gasoline in kg /L n_o=0.3;// The over all efficiency of the engine C_dc=1.1;// The drag coefficient for a circular disk C_dh=0.4;//The drag coefficient for a hemispherical body HV=44000;// The heating value of gasoline in kJ/kg // Given values V=95;// km/h Pr=0.60;//Price of gasoline in $/L D=0.13;// m L=24000;// km/year //Calculation A=(%pi*0.13^2)/4;//m^2 F_d=(C_dc*A*rho_a*V^2)/(2*3.6^2);//The drag force acting on the flat mirror in N W_drag=F_d*L;// kJ/year E_in=W_drag/n_o;// kJ/year m_f=E_in/HV; // kg/year Amount=m_f/rho_g;// L/year Cost=(Amount*Pr);// $/year Rr=(C_dc-C_dh)/C_dc;// Reduction ratio Fr=Rr*Amount;// Fuel reduction in L/year printf('Fuel reduction =%0.2f L/year\n',Fr); Cr=Rr*Cost;// Cost reduction in $/year printf('Cost reduction =%0.2f $/year\n',Cr); // The answer vary due to round off error