UN Fisika 2016 Paket 1 Nomor 15

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15

Sebuah bola sedang meluncur menuruni lintasan licin. Bila laju benda di titik A sama dengan 6 m.{{s}^{-1}} dan g = 10 m.{{s}^{-2}}, laju benda di titik B adalah …

A.    \sqrt{52}~~m.{{s}^{-1}} D. \sqrt{95}~~m.{{s}^{-1}}
B.     \sqrt{65}~~m.{{s}^{-1}} E. \sqrt{128}~~m.{{s}^{-1}}
C.     \sqrt{92}~~m.{{s}^{-1}}

Penyelesaian

Berlaku hukum kekekalan energi mekanik

E{{M}_{0}}=E{{M}_{t}}

mg{{h}_{0}}+\frac{1}{2}mv_{0}^{2}=mg{{h}_{t}}+\frac{1}{2}mv_{t}^{2}

g{{h}_{0}}+\frac{1}{2}v_{0}^{2}=g{{h}_{t}}+\frac{1}{2}v_{t}^{2}

\frac{1}{2}v_{0}^{2}+g{{h}_{0}}-g{{h}_{t}}=\frac{1}{2}v_{t}^{2}

{{v}_{t}}=\sqrt{2\left( \frac{1}{2}v_{0}^{2}+g({{h}_{0}}-{{h}_{t}}) \right)}

{{v}_{t}}=\sqrt{2\left( \frac{1}{2}{{\left( 6 \right)}^{2}}+10(5,6-1) \right)}

{{v}_{t}}=\sqrt{128}~m.{{s}^{-1}}

jawaban E

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