Answer:
The additional force is [tex]F_3 = 120 \ N[/tex]
Explanation:
From the question we are told that
The horizontal force in one direction is [tex]F_i = 480 \ N[/tex]
The horizontal force in the opposite direction is [tex]F_f = -600 \ N[/tex]
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
[tex]F_1 + F_2 +F_3 = 0[/tex]
Where [tex]F_3[/tex] is the additional force required
So
[tex]F_3 = -F_1 - F_2[/tex]
substituting values
[tex]F_3 = -480 - [-600][/tex]
[tex]F_3 = -480 + 600[/tex]
[tex]F_3 = 120 \ N[/tex]
