A particle starts from origin at $t = 0$ with a velocity $5 \hat{i}\text{ m/s}$ and moves in x-y plane under action of a force which produces a constant acceleration of $(3\hat{i} + 2\hat{j})\text{ m/s}^2$. If the x-coordinate of the particle at that instant is $84\text{ m}$, then the speed of the particle at this time is $\sqrt{\alpha}\text{ m/s}$. The value of $\alpha$ is ___________.