To the Ineffable All,
I can only think of one way to measure tall structures with a yardstick, 100 ft cord, and 'scope. Go to the end of the structure's shadow. Place the o'scope at that point. Immediately, prop up the yardstick vertically and measure the lenth of its shadow. Measure the distance from the 'scope to the building with the yardstick and extension cord. Solve for the height of the structure by proportional triangles.
The balloon will go backwards because the deceleration will cause the weight of the air to have a forward component. Since a helium balloon travels in the opposite direction of the air weight, it will go backwards.
These two "problems", along the the R-cube are really puzzles. That means they are contrived problems with little or no practical use in the real world. If I were an employer, I would like to see whether someone could do a real world problem.
Ratch