Given data
*The weight of the box is W = 500 N
*The distance of the plank from the fulcrum is d = 5 m
*The given force at a distance from the fulcrum is D = 10 m
The minimum force is required to lift the box is given by the net torque as
[tex]\begin{gathered} \tau=0 \\ W\times d-F\times D=0 \\ W\times d=F\times D \end{gathered}[/tex]Substitute the known values in the above expression as
[tex]\begin{gathered} 500\times5=F\times10 \\ F=250\text{ N} \end{gathered}[/tex]Hence, the minimum force is required to lift the box is F = 250 N