## Fundamentals of Physics Extended (10th Edition)

F acts in positive $x$ direction
Work done by the force is is equal to negative change in potential Energy : $W=-\Delta U=-\left( U_{B}-U_{A}\right) =-20J=F\times \Delta x=F\times \left( 2-4\right) =F\times \left( -2\right) \Rightarrow$ This leads to: $F=10N$ We see that $F$ is positive so it acts in positive $x$ direction.