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# CHAPTER 2 Problem 103

<span class="room-tag">If a baseball pitcher throws a fastball at a horizontal speed of 160 km/h, how long does the ball take to reach home plate 18.4 m away?</span>

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將運動過程視為等速度運動，故
\begin{aligned}
\Delta x = v\times \Delta t \Longrightarrow \Delta t = \frac{\Delta x }{v}
\end{aligned}
<br>

將題目提供之數值代入，得到
\begin{aligned}
\Delta t = \frac{\Delta x }{v}=\frac{18.4 \ \mathrm{m}}{160 \ \mathrm{km/h}}=\frac{18.4 \ \mathrm{m}}{160 \times \frac{1000 \ \mathrm{m}}{3600 \ \mathrm{s}}}\approx 0.414 \ (\mathrm{s}) =414 \ (\mathrm{ms})
\end{aligned}
<br>

###### tag: `Fundamentals of Physics`