Question

In a race, a runner traveled 12 meters in
4.0 seconds as she accelerated uniformly from
rest. The magnitude of the acceleration of the
runner was
(1) 0.25 m/s2 (3) 3.0 m/s2
(2) 1.5 m/s2 (4) 48 m/s2

Answer 1

     Since it is a race, the runner start from rest, so we can use the Velocity Hourly Equation to describle yours moviment.

$S=S_{o}+V_{o}t+ \frac{at^2}{2} \\ S=\frac{at^2}{2}$
 
     Entering the unknowns, we have:

$S=\frac{at^2}{2} \\ 12*2=a*4^2 \\ \boxed {a=1.5m/s^2}$

Number 2

If you notice any mistake in my english, please let me know, because i am not native.