Answer: No force is required to keep the mass moving at a constant velocity (on a frictionless surface) and in the same direction
Step-by-step explanation:
Tricky question!
The force required to slow the moving mass down to a rest is F = ma
F = (6 kg) x ((0 - 8m/s)/(3 s)) = 16 N (force in opposite direction of motion)
To keep the 6 kg mass which is already moving at a velocity of 8 m/s going in the same direction at the same velocity, no force (F=0) is applied, due to Newton's 1st Law of Motion. This assumes a frictionless surface.