Question

question 28
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a runner maintains constant acceleration after starting from rest as she runs a distance of 60.0 m. the runners speed at the end of the 60.0 m is 9.00 m/s. how much time did it take the runner to complete the 60.0 m distance?
10.2 s
9.80 s
6.67 s
13.3 s
15.0 s

Explanation:

Step1: Find the average speed

The average speed formula for constant - acceleration motion starting from rest is \(v_{avg}=\frac{v_{i} + v_{f}}{2}\). Given \(v_{i} = 0\ m/s\) and \(v_{f}=9.00\ m/s\), then \(v_{avg}=\frac{0 + 9.00}{2}=4.50\ m/s\).

Step2: Calculate the time

We know that the formula for average speed is \(v_{avg}=\frac{d}{t}\), where \(d = 60.0\ m\) and \(v_{avg}=4.50\ m/s\). Rearranging for \(t\), we get \(t=\frac{d}{v_{avg}}\). Substituting the values, \(t=\frac{60.0}{4.50}\approx13.3\ s\).

Answer:

13.3 s