What additional force is needed?

Question

A horizontal force of 350 N is applied to a stationary wooden box in one direction, and a 700 N horizontal force is applied in the opposite direction. What additional force is needed for the box to remain stationary?
 ____ N

Answer 1

In order for the box to be stationary, the sum of all forces must equal to zero.  This is due to Newton's first law of motion.  

 

 

Let   F₁ = 350

       F₂ = -700              (negative sign indicates opposite direction)

       F₃  is the unknown force

 

Our equation is

 

F₁ + F₂ + F₃ = 0

350 - 700 + F₃ = 0

-350 + F₃ = 0

           F₃ = 350

 

An additional force of 350 N in the same direction of the initial 350 N force is needed.