Horizontal Force to Hold Pendulum Perpendicular

[derek88]

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...?

 

[daqddyo1]

Well, if theta = 90 degrees, then tan (theta) is infinite which suggests that the wind speed required would also have to be infinite.
In reality, there is no windspeed that would make the pendulum line horizontal. The angle will always be less than 90 degrees because gravity is always pulling down on the bob.

 

[Lsos]

Electrical wires are also NEVER horizontal. They always droop. Even a taught string, though it appears perfectly straight, isn't. There has to be a vertical component to the force holding it up, and that vertical somponent comes from the angle.

 

[Low-Q]

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...?

You can allways shape the mass as a wing so the passing wind makes sub-pressure above it in order to lift the mass the last degrees until the pendulum rest at 90 degrees. However, that will also mean that the wind change direction when passing the mass/wing - meaning the wind will not move stright horizontal, but slightly downwards around the wing.

Vidar

 

[asteriatic]

I would like to provide a response to this content by saying that the equation provided is indeed correct. The angle that the pendulum makes with the vertical is determined by the ratio of the horizontal force applied to the weight of the pendulum. This means that a sustained force of FH will indeed keep the pendulum at a certain angle theta. However, it is important to note that there are other factors that may affect the pendulum's movement, such as air resistance and the length of the pendulum's string. Additionally, the force required to hold the pendulum at a specific angle may vary depending on the initial conditions and the environment in which the pendulum is placed. It is always important to consider all variables and factors when solving scientific problems.