A horizontal force of 480 n is applied to a stationary wooden box in one direction and a 600 n horizontal force is applied in the opposite direction. What is the additional force is needed for the box to remain stationary

The additional force is  

Explanation:

From the question we are told that

      The horizontal force in one direction is  

       The horizontal force in the opposite direction is  

The negative sign shows that it is acting in the opposite direction

Generally for the box to remain stationary the net force on it must be equal to zero  that is  

Where is the additional force required  

    So

substituting values

prolly a beacuse the momentuem the car has increases while going down hill