c) CA = CB = 5 cm

Trả lời

c)

$CA=CB=5cm$

$\text{cos}\alpha \text{=}\frac{5^2+5^2-6^2}{\mathrm{2.5.5}}=\frac{7}{25}$

$F_3^2=F_1^2+F_2^2+2.F_1{F}_2\text{cos}\beta$

$F_3^2=2F_1^2+2F_1^2(-c\text{os}\alpha \text{)}$

$F_3^2=2F_1^2\left(1-c\text{os}\alpha \right)=2$

$F_3=F_1\sqrt{2\left(1-c\text{os}\alpha \right)}=k\frac{q_1{q}_3}{r^2}\sqrt{2\left(1-c\text{os}\alpha \right)}$

$F_3={9.10}^9.\frac{{\left({8.10}^{-8}\right)}^2}{0,{05}^2}\sqrt{2\left(1-\frac{7}{25}\right)}=0,028\left(N\right)$