Question 532701
<pre>
v<sub>f</sub> = v<sub>0</sub> + at

where v<sub>f</sub> = final velocity
and v<sub>0</sub> = initial velocity
and a = acceleration
and t = time in seconds

We solve it for t

at = v<sub>f</sub> - v<sub>0</sub>

t = {{{(v[f]-v[0])/a}}}

The speed of light is 299792458 m/s, 90% of that is 269813212.2 m/s
so that will be v<sub>f</sub>.

We will assume starting from rest so we will use v<sub>0</sub> = 0

1 G is the acceleration = 9.81 m/sē,

we substitute in 

t = {{{(v[f]-v[0])/a}}}

t = {{{(269813212.2-0)/9.81}}}

t = 27503895.2 seconds = 458398.3 hours = 19099.9 days = 52.3 years.

Edwin</pre>