Acceleration 3503

What speed was the car moving until the driver started braking when it moved with a constant acceleration a = -1.2m/s² during braking until it stopped, traveling a distance of 135m?

Correct answer:

v =  18 m/s

Step-by-step explanation:

$$\begin{gathered} s=135\text{m} \\ a=1.2{\text{m/s}}^2 \\ s=\frac{1}{2}\cdot a\cdot t^2 \\ t=\sqrt{2\cdot s/a}=\sqrt{2\cdot 135/1.2}=15\text{s} \\ v=a\cdot t=1.2\cdot 15=18\text{m/s} \end{gathered}$$

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