# An aircraft lands and brakes, slowing from 250 m/s to 5 m/s in 30 secs. What is its acceleration?

May 26, 2018

$8.17 {\text{ m s}}^{-} 2$

#### Explanation:

$a = \frac{v - u}{t}$ where

$a$ is acceleration
$v$ is final velocity
$u$ is intial velocity
$t$ is time.

$a = \frac{5 - 250}{30}$
$= - \frac{245}{30}$
$= - \frac{49}{6} {\text{ m s}}^{-} 2$
$\approx 8.17 {\text{ m s}}^{-} 2$

May 26, 2018

$- 8.16$ $m {s}^{-} 2$

#### Explanation:

To solve this, we use the formula

color(blue)(a=(v-u)/t

Where, $a$ is the acceleration, $v$ is the final and $u$ the initial velocities.And, $t$ is the time taken

So, here, initial velocity is $250 \frac{m}{s}$ and final velocity is $5 \frac{m}{s}$ and the time taken is $30 s$

$\rightarrow a = \frac{5 - 250}{30}$ $m {s}^{-} 2$

$\rightarrow a = - \frac{245}{30} m {s}^{-} 2$

$\rightarrow a = - \frac{49}{6} m {s}^{-} 2$

color(green)(rArra~~-8.16 color(green)(ms^-2

Note: here the value is negative, so the plane is decelerating(opposite of accelerating). So, this is known as deceleration.

Hope that helps...$\phi$