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Answer 1

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¹ÊÆä¼ÓËٶȵĴóСΪ$4.5m/{s}_{\;}^{2}$
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${t}_{1}^{\;}=\frac{s-{s}_{1}^{\;}}{{v}_{1}^{\;}}=\frac{50-25}{15}s=\frac{5}{3}s$
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${t}_{2}^{\;}=\frac{0-{v}_{1}^{\;}}{{a}_{1}^{\;}}=\frac{10}{3}s$
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${t}_{3}^{\;}=\frac{{v}_{2}^{\;}-{v}_{3}^{\;}}{{a}_{2}^{\;}}=\frac{6-1}{2.5}s=2s$
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${s}_{2}^{\;}=\frac{{v}_{2}^{\;}+{v}_{3}^{\;}}{2}{t}_{3}^{\;}=7m$
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${t}_{4}^{\;}=\frac{s-{s}_{2}^{\;}}{{v}_{2}^{\;}}=\frac{50-7}{6}=7.2s$
${t}_{1}^{\;}+{t}_{2}^{\;}£¼{t}_{3}^{\;}+{t}_{4}^{\;}£¼{t}_{1}^{\;}+{t}_{2}^{\;}+10s$
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