Traffic collision

When investigating a traffic accident, a policeman found that the driver stopped the vehicle immediately after the accident by constantly braking on a 150 m track in 15 seconds. Do you approve that the driver exceeded the village's permitted speed (50 km/h) before braking?

Correct answer:

v =  72 km/h

Step-by-step explanation:

$$\begin{gathered} s=150\text{m} \\ t=15\text{s} \\ s=a{t}^2/2 \\ a=2\cdot s/t^2=2\cdot 150/15^2=\frac{4}{3}\doteq 1.3333{\text{m/s}}^2 \\ {v}_1=a\cdot t=1.3333\cdot 15=20\text{m/s} \\ v=3.6\cdot v_1=3.6\cdot 20=72=72\text{km/h} \\ v>50km/h \end{gathered}$$

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