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Q103P

Expert-verifiedFound in: Page 39

Book edition
10th Edition

Author(s)
David Halliday

Pages
1328 pages

ISBN
9781118230718

**Question: If a baseball pitcher throws a fastball at a horizontal speed of 160 Km/hr****, ****how long does the ball take to reach home**** plate 18.4 m**** away?**

The time taken by ball to reach home plate is $414\text{m/s}$ .

The speed of the ball is $160\text{km/h}$ .

The distance of the plate is $18.4\text{m}$ .

** **

**The speed of an object is defined as the rate of change of distance with time. It is a scalar quantity. **

The expression for the speed is given as follows:

$\text{Distance= Speed\xd7Time interval}$ … (i)

First, convert the speed of the ball from $\text{km/h}$ to$\text{m/s}$ .

The speed of the ball can be written as,

$\text{Speed = 160 km/h}\phantom{\rule{0ex}{0ex}}=160\times \frac{5}{18}\text{m/s}\phantom{\rule{0ex}{0ex}}=44.44\text{m/s}$

From equation (i), the time taken by ball is calculated as follows:

role="math" localid="1650526041222" $\text{Time interval =}\frac{\text{Distance}}{\text{Speed}}\phantom{\rule{0ex}{0ex}}\text{=}\frac{18.4\text{m}}{44.44\text{m/s}}\phantom{\rule{0ex}{0ex}}=\text{0.414 s}\phantom{\rule{0ex}{0ex}}=414\text{ms}$

Thus, the time taken by ball to reach home plate is $414\text{ms}$ .

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