Acceleration 7071

A tractor travels along a straight road at a speed of 15 m/s. The tractor driver starts braking with an acceleration of 2 m/s². Specify

a) the magnitude of the speed and the path of the tractor in 5 s from the moment it started to brake
b) the time for which he stops.

Correct answer:

v =  5 m/s
s =  50 m
t₂ =  7.5 s

Step-by-step explanation:

$$\begin{gathered} v_1=15\text{m/s} \\ {v}_2=0\text{m/s} \\ a=-2{\text{m/s}}^2 \\ {t}_1=5\text{s} \\ v=v_1+a\cdot t_1=15+(-2)\cdot 5=5\text{m/s} \end{gathered}$$

$s=v_1\cdot t_1+\frac{1}{2}\cdot a\cdot t_1^2=15\cdot 5+\frac{1}{2}\cdot (-2)\cdot 5^2=50\text{m}$

$t_2=(v_2-v_1)/a=(0-15)/(-2)=7.5\text{s}$

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