M=13 кг R=0.5 Ом po1=15*10^-8 Ом*м po2=7.8*10^3 кг/м3 L=?
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m=po2*V=po2*L*S
S=m/(po2*L)
R=po1*L/S=po1*po2*L²/m
L=√(R*m/(po1*po2))=√(0.5*13/(15*10^-8*7.8*10^3))=74.5 м
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S = v₀t+at²/2
1. v₀t=S-at²/2 ⇒
v₀=(S-at²/2)/t = S/t-at/2
2. at²/2=S-v₀t ⇒
at²=2(S-v₀t) ⇒
a= 2(S-v₀t)/t²
Г=f/d=80/2=40
f=40*d
1/d+1/f=D
(f+d)/f*d=D
(40*d+d)/40*d*d=D
41*d/40*d^2=D D=1,025/d=1,025/0,205=5 дптр