Question

am nevoie urgent de problemele 10 si 11, PHI 2015, clasa a 8-a, cu rezolvare mulțumesc sau să mi spuneți unde o pot găsi

Answer 1

[tex]10)Se~da:\\ \\ c_{Al}=919,6\frac {J}{kgK}\\ \\ m_1=500g=0,5kg\\ \\ m_2=3kg\\ \\ c_{apa}=4185\frac{J}{kgK}\\ \\ t_1=20^\circ\\ \\ t_f=100^\circ\\ \\ \eta=40\%=0,4\\ \\ q=4598\times 10^4\frac{J}{kg}\\ \\ m=?g\\ \\ \\ [/tex]


[tex]\eta=\large\frac{Q_u}{Q_t}\\ \\ \\ Q_u=Q_1+Q_2\\ \\ Q_u=c_{Al}\times m_1\times(t_f-t_1)+c_{apa}\times m_2\times(t_f-t_1)\\ \\ Q_u=(t_f-t_1)\times(c_{Al}\times m_1+c_{apa}\times m_2)\\ \\ \\ Q_t=q\times m [/tex]


[tex]\eta=\frac{(t_f-t_1)\times(c_{Al}\times m_1+c_{apa}\times m_2)}{q\times m}\\ \\ m=\long\frac{(t_f-t_1)\times(c_{Al}\times m_1+c_{apa}\times m_2)}{q\times \eta}\\ \\ \\ Calcule:\\ \\ m=\frac{(100-20)\times(919,6\times 0,5+4185\times 3)}{4598\times 10^4\times 0,4}=0,0566kg=56,6g[/tex]




[tex]11)Se~da:\\ \\ c_{gheta}=2090\frac{J}{kgK}\\ \\ \lambda_{gheata}=33,5\times 10^4\\ \\ m_1=m_2=m=100g=0,1kg\\ \\ t_1=-20^\circ\\ \\ t_2=0^\circ\\ \\ \Delta Q=?\\ \\ \\[/tex]


[tex]Formule:\\ \\ \Delta Q=Q_1-Q_2\\ \\ \\ Q_1=Q_{incalzire}+Q_{topire}\\ \\ Q_1=c_{gheata}\times m\times(t_2-t_1)+m\times \lambda_{gheata}\\ \\ \\ Q_2=Q_{topire}\\ \\ Q_2=m\times \lambda_{gheata}\\ \\ \\[/tex]


[tex]\Delta Q=c_{gheata}\times m\times(t_2-t_1)+m\times \lambda_{gheata}-m\times \lambda_{gheata}\\ \\ \Delta Q=c_{gheata}\times m\times(t_2-t_1)\\ \\ \\ Calcule:\\ \\ \Delta Q=2090\times 0,1\times(0+20)=4180J=4,18kJ [/tex]