We can use the motion formula:
![v=u+at](https://img.qammunity.org/2023/formulas/mathematics/high-school/noa8ap485tcbqe59xpwvgja2yjtndl0d9d.png)
Where
v is the final velocity
u is the initial velocity
a is the acceleration
t is the time
Now, given,
a = 1.5
t = 3
u = 0 (starts at rest)
v = ???
We will substitute the values into the equation of motion and find the final velocity (final speed).
![\begin{gathered} v=u+at \\ v=0+(1.5)(3) \\ v=0+4.5 \\ v=4.5 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/z2zo5dxeaqhecj6fxdj7esboby8jltpako.png)
So the final speed is 4.5