Resposta :
a)
(coeficiente de dilatação superficial) = 2(coeficiente de dilatação linear)
ΔA=Ao.b.ΔT
ΔA=(0,3*0,4).2.10^-6.(80-20)
ΔA=1,44.10^-5 m^2
b) ΔA=Af-Ao
1,44.10^-5=Af-0,12
Af=1,44.10^5 + 0,12
Af=12001,44.10^-5
Af=1200,144 cm^2
(coeficiente de dilatação superficial) = 2(coeficiente de dilatação linear)
ΔA=Ao.b.ΔT
ΔA=(0,3*0,4).2.10^-6.(80-20)
ΔA=1,44.10^-5 m^2
b) ΔA=Af-Ao
1,44.10^-5=Af-0,12
Af=1,44.10^5 + 0,12
Af=12001,44.10^-5
Af=1200,144 cm^2