Acceleration 80626

The car stopped at an initial speed of 90 km/h on a track of 62.5 m. What was its acceleration, and how long did it take to brake the car?

Correct answer:

a =  -5 m/s²
t =  5 s

Step-by-step explanation:

$$\begin{gathered} v_1=90\text{km/h}\to \text{m/s}=90:3.6\text{m/s}=25\text{m/s} \\ {v}_2=0\text{m/s} \\ s=62.5\text{m} \\ v=\frac{v_1+v_2}{2}=\frac{25+0}{2}=\frac{25}{2}=12.5\text{m/s} \\ t=s/v=62.5/12.5=5\text{s} \\ a=\frac{v_2-v_1}{t}=\frac{0-25}{5}=-5{\text{m/s}}^2 \end{gathered}$$

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