The International System Units or the SI units is scientific method of expressing the magnitudes or quantities of important natural phenomena. There are seven base units in the system, from which other units are derived. This system was formerly called the meter-kilogram-second (MKS) system.
The free-body diagram of the forces acting on the flag is in the picture in attachment.
We have: the weight, downward, with magnitude

the force of the wind F, acting horizontally, with intensity

and the tension T of the rope. To write the conditions of equilibrium, we must decompose T on both x- and y-axis (x-axis is taken horizontally whil y-axis is taken vertically):


By dividing the second equation by the first one, we get

From which we find

which is the angle of the rope with respect to the horizontal.
By replacing this value into the first equation, we can also find the tension of the rope:
The problem you would encounter is measuring the height of two different people, a tall one and a short one, and getting the same answer for both of them.
No matter WHAT we're hearing out of the White House these days, you CAN'T bend and stretch your standard measuring devices, or any other 'facts', to make them fit the thing that you're measuring. This does not work. You're always entitled to your own opinions, but you're not entitled to your own facts.
Power = energy / time
Time should be in seconds
5 hours = 5 × 60 minutes = 5 × 60 ×60 seconds = 18000 s
Power = 6000/18000 = 0.333 W
Hope it helped!