Calculate the time required for a 6000.-newton net force to stop a 1200.-kilogram car initially traveling at 10. m/s

               Force = (mass) x (acceleration).

We know the force and the mass, so we can write

               6,000 N = (1,200 kg) x (acceleration).

Divide each side by 1,200 kg:       

               Acceleration = 6000N/1200kg = 5 m/s² .

That's the acceleration.  The car's speed changes by 5 m/s each second
that the force acts on it.  If the force pushes from behind, then the car goes
5 m/s faster every second.  If the force pushes from in front, then the car
goes 5 m/s slower every second.

The car is moving at 10 m/s and we want to slow it down to zero m/s.  So
the force has to push from the front, and it will take  (10/5) = 2 seconds to
complete the job.