Answer:
4.67 N of force are required
Step-by-step explanation:
The second Newton's law states the net force exerted on a body of mass m that has an acceleration a, is given by:
F=m.a
On the other hand, the kinematics equations relate the acceleration with the change of speed over time, expressed as:

We are given the initial speed of vo=4 m/s on a mass of m=3.5 Kg, the final speed of vf=8 m/s which took t=3 seconds.
The acceleration is:


Thus, the force is:


4.67 N of force are required