Question

A jet plane lands with a speed of 108 m/s and can accelerate at a maximum rate of −4.90 m/s2 as it comes to rest.(a) From the instant the plane touches the runway, what is the minimum time needed before it can come to rest?________ s

Answer 1

We will determine the time needed to fuly stop as follows:

$v_f=v_i+at$

Then:

$\begin{gathered} 0m/s=108m/s+(-4.90m/s^2)t\Rightarrow(-4.90m/s^2)t=-108m/s \\ \\ \Rightarrow t=\frac{1080}{49}s\Rightarrow t\approx22.0s \end{gathered}$

So, the minimim time is 1080/49 s, that is approximately 22.0 s.