As it is given that the air bag deploy in time
[tex]t = 10 ms = 0.010 s[/tex]
total distance moved by the front face of the bag
[tex]d = 20 cm = 0.20 m[/tex]
Now we will use kinematics to find the acceleration
[tex]d = v_i*t + \frac{1}{2}at^2[/tex]
[tex]0.20 = 0 + \frac{1}{2}a*0.010^2[/tex]
[tex]0.20 = 5 * 10^{-5}* a[/tex]
[tex]a = 4000 m/s^2[/tex]
now as we know that
[tex]g = 10 m/s^2[/tex]
so we have
[tex]a = 400g[/tex]
so the acceleration is 400g for the front surface of balloon