Chapter 2, Problem 70A

(a)

To determine

To Describe:A story that will determine the person’s movement along a straight path as represented by the graph.

Explanation of Solution

J runs with a constant speed between the trees.

First, he runs at a speed of $1\text{m/s}$ for $6$ seconds. Then, he stops for $18$ seconds and again started running at a speed of $\frac{4}{3}$ m/s. After taking rest of around $5$ seconds, he decided to come back by same way. He runs at a speed of $\text{1}\text{m/s}$ for $9$ seconds and stops for $5$ seconds. Then he covered next $3$ m in just $1$ second and rests for $4$ seconds. He then comes to the start point at a speed of $\frac{4}{3}$ m/s.

(b)

To determine

Time at which J is $6$ m away from the origin.

Answer to Problem 70A

Explanation of Solution

By reading the graph carefully one can calculate the time easily.

x -axis has an interval of $5$ seconds. y -axis has the interval of $2$ seconds.J takes $6$ seconds to reach at $6$ m away from the origin.

(c)

To determine

Time in which J reaches $12$ m from the origin.

Explanation of Solution

From the graph, it is clear that Jreaches $12$ m from the origin in $32$ seconds.

(d)

To determine

Average velocity between $37.0$ s and $46.0$ s.

Answer to Problem 70A

$-1\text{m/s}$

Explanation of Solution

Given:

From the graph, average velocity can be calculated.

Net displacement, $-9\text{ m}$

Total time taken, 9 s

Formula used:

Average velocity $\text{=}\frac{\text{Net Displacement}}{\text{Total}\text{time}}$

Calculations:

Average velocity

  $\begin{array}{l}=\frac{-9}{9}\text{m/s}\\ =-1\text{m/s}\end{array}$