A car starts from rest and accelerates uniformly at $2$ m s$^{-2}$. What is its velocity after $5$ s?

Using $v = u + at$ with $u = 0$: $v = 0 + 2 \times 5 = 10$ m s$^{-1}$. The value 25 m is the distance covered ($\frac{1}{2}at^2$), not the velocity.