a,*Rót 1 ca nước từ bình 1 sang bình 2
\(=>Qthu\)(nước bình 1)\(=m1.Cn.\left(tc2-20\right)\left(J\right)\)
\(=>Qtoa\)(nước bình 2)\(=4.Cn\left(60-tcb2\right)\left(J\right)\)
\(=>m1.Cn.\left(tcb2-20\right)=4Cn\left(60-tcb2\right)\left(1\right)\)
*Rót 1 ca nước từ bình 2 sang bình 1
\(=>Qthu\)(nước bình 1)\(=\left(2-m1\right)Cn\left(21,95-20\right)\left(J\right)\)
\(=>Qtoa\)(nước bình 2)\(=m1.Cn\left(tcb2-21,95\right)\left(J\right)\)
\(=>\left(2-m1\right)Cn\left(21,95-20\right)=m1.Cn\left(tcb2-21,95\right)\left(2\right)\)
lấy(2) chia(1)\(=>\)hệ pt
\(=>\left\{{}\begin{matrix}\left(2-m1\right)1,95=m1\left(tcb2-21,95\right)\\m1\left(tcb2-20\right)=4\left(60-tcb2\right)\end{matrix}\right.\)
\(=>\left\{{}\begin{matrix}20m1-m1.tcb2=-3,9\left(3\right)\\-20m1+m1.tcb2=240-4tcb2\left(4\right)\end{matrix}\right.\)
lấy(3) cộng (4)
\(=>-3,9+240-4tcb2=0=>tcb2=59,025^oC\left(5\right)\)
thế(5) vào(1)\(=>m1\left(59,025-20\right)=4\left(60-59,025\right)=>m1\approx0,01kg\)
b, tiếp tục làm như thế lần 2
* rót 1 ca nước từ bình 1 sang bình 2 , nước trong ca là 0,1kg
\(=>Qthu1=0,1.4200\left(tcb3-21,95\right)\left(J\right)\)
\(=>Qtoa2=\)\(4Cn\left(59,025-tcb3\right)\)(J)
\(=>0,1\left(tcb3-21,95\right)=4\left(59,025-tcb3\right)=>tcb3\approx58^OC\)
