Tổng hợp lực \(\overrightarrow{F}\)
\(\overrightarrow{F}=\overrightarrow{F_1}+\overrightarrow{F_2}+\overrightarrow{F_3}\)
\(\Rightarrow F^2=F_1^2+F_2^2+F_3^2+2\left(\overrightarrow{F_1}.\overrightarrow{F_2}+\overrightarrow{F_2}.\overrightarrow{F_3}+\overrightarrow{F_1}.\overrightarrow{F_3}\right)\)
\(\Rightarrow F^2=3F_1^2+2\left(F_1^2.cos60^o+F_1^2.cos60^o+F_1.cos90^o\right)\left(F_1=F_2=F_3=15\left(N\right)\right)\)
\(\Rightarrow F^2=3F_1^2+2.2F_1^2.\dfrac{1}{2}=5F_1^2=5.15^2\)
\(\Rightarrow F=15\sqrt{5}\approx33,54\left(N\right)\)
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