UN Fisika 2016 Paket 3 Nomor 31

Tiga muatan titik terletak pada titik-titik sudut segitiga, seperti pada gambar.

31

Besar gaya coulomb pada titik A adalah … \left( k=9\times {{10}^{9}}~N.{{m}^{2}}.{{C}^{-2}}~;1~\mu ={{10}^{-6}} \right)

A.    10 N D.    90\sqrt{2} N
B.     60 N E.     100\sqrt{2} N
C.     90 N

Penyelesaian

Karena ketiga muatan sama besar, {{F}_{21}}={{F}_{31}}=F

31-kunci

{{F}_{12}}=\frac{k{{q}_{1}}{{q}_{2}}}{{{r}_{12}}}=\frac{\left( 9\times {{10}^{9}} \right)\left( 4,5\times {{10}^{-6}} \right)\left( 2\times {{10}^{-6}} \right)}{{{\left( 3\times {{10}^{-2}} \right)}^{2}}}=90~N

{{F}_{32}}=\frac{k{{q}_{3}}{{q}_{2}}}{{{r}_{12}}}=\frac{\left( 9\times {{10}^{9}} \right)\left( 8\times {{10}^{-6}} \right)\left( 2\times {{10}^{-6}} \right)}{{{\left( 4\times {{10}^{-2}} \right)}^{2}}}=90~N

{{F}_{12}}={{F}_{32}}=F

 

Resultan gaya R

R=\sqrt{{{F}^{2}}+{{F}^{2}}}=F\sqrt{2}

R=90\sqrt{2}

jawaban D

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