As a vehicle approaches a stop sign, the driver applies the brakes and brings the vehicle to a stop. How is this action explained using Newton’s Second Law?

Newton’s 2nd Law talks of changes in momentum. If a moving car comes to a stop it’s momentum has certainly changed so a Force has acted on it. Because the change of momentum is negative the Force is in the opposite direction to the motion. The time taken will determine the size of the force. The shorter the time the bigger the force.