Answer
$a = 13~m/s^2$
Work Step by Step
Relative to the crew member standing on the ground, the cheetah is moving $50~km/h$ west and then $45~km/h$ east
The magnitude of the change in velocity is $95~km/h$
We can express $95~km/h$ in units of $m/s$:
$(95~km/h)(\frac{1~h}{3600~s})(\frac{1000~m}{1~km}) = 26.4~m/s$
We can find the magnitude of the acceleration according to the nervous crew member:
$a = \frac{\Delta v}{\Delta t}$
$a = \frac{26.4~m/s}{2.0~s}$
$a = 13~m/s^2$
