H=30 см d=80 см D=5 дптр f=? H=?
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F=1/D=1/5=0.2 м (20 см)
1/F=1/d+1/f
f=F*d/(d-F)=20*80/(80-20)=27 см
H/h=f/d
H=f*h/d=27*30/80=10 см
======================
4)
t1=S/(v+u)
t2=S/(v-u)
t=t1+t2=S/(v+u)+S/(v-u)=2Sv/(v^2-u^2)=2*144000*(18/3,6)/((18/3,6)^2-3^2) сек=<span>
90000
</span>сек = <span>
1500
</span>мин = 25 час
5)
A=m*g*h=P*t
P=m/t*g*h=ro*(V/t)*g*h=1000*(4,5/60)*10*100 Вт =<span>
75000
</span>Вт = 75 кВт
Решение:
m=Q/q=1000000/1000000=1 кг
L1m1=L2m2
L2/L1=m1/m2
L2/L1=P1L1/(P2*L2)
(L2/L1)^2=1/2
L2/L1=1/SQRT(2)=0,71
R=U/I
R=ρ*L/s
L=R*s/ρ=(U/I)*(s/ρ)
L=(22B/5A)*(0,02мм²/<span> 1,1 Ом⋅мм</span>²<span>/м)=0,8м=80см</span>