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F=Fтр1+Fтр2=μ1mg+μ2(M+m)g=0.6*5*10+0.2*10*(5+20)=30+60=90[H]
Fтр1=<span>μ1mg
Fтр2=</span><span> μ2(M+m)g</span>
1)Q=cm(t2-t1)=2060*5*8=82.6кДж
2)Q=cmt(t2-t1)=1005*5*77.4=388935Дж=388,935кДж
0,8=R/R+r
0,8*R+0,8*r=R
R=0,8*r/0,2=4 Ом
E=I*R+I*r=2*4+2*1=10 В