Good morning.
We have that:
[tex]\mathsf{V = a\cdot t}[/tex] , since we have rest in the inicial time.
The acceleration can be found with Newton's Law:
[tex]\mathsf{F = m\cdot a\iff a = \dfrac{F}{m}} [/tex]
Now we put the acceleratin in the velocity equation:
[tex]\mathsf{V = \dfrac{F}{m} \cdot t}[/tex]
We want the force, so, let's isolate F:
[tex]\mathsf{V\cdot m = F\cdot t}\\ \\ \\ \boxed{\mathsf{F = \dfrac{V\cdot m}{t}}}[/tex]
