Friends: Recently I got this problem: what sustained horizontal wind pressure/force is needed to make a pendulum swing up and stay at a certain angle? To solve this problem, I imagined applying a horizontal force FH to the bob (of mass "m"). I learned that the angle that the pendulum makes with the vertical (denoted as "theta") is found by solving: tan (theta) = FH / mg Is this correct? Does this mean that a sustained force of FH will keep the pendulum at the angle theta? Because the equation seems to imply that you need an infinite FH to make the pendulum horizontal, i.e. theta = 90 degrees. Weird...?