Why specifically should a Foucault pendulum be long and massive?

Question

For a pendulum to easily demonstrate the Foucault effect, it should have as long a cable as possible (this one is 52 feet) and a heavy symmetrical bob (this one is hollow brass, weighing about 240 pounds).

https://www.si.edu/spotlight/foucault-pendulum#:~:text=Any%20pendulum%20consists%20of%20a%20cable%20or%20wire,one%20is%20hollow%20brass%2C%20weighing%20about%20240%20pounds%29.

Question

Why specifically should a Foucault pendulum be long and massive? Is it simply because of air resistance? If so, could I make a small but effective one in an evacuated glass jar?

Assumption

To keep the Foucault Pendulum going, one must replace the energy lost with each swing. This can be done by giving the pendulum a little "kick" with each swing.

To do this, two iron collars are attached to the cable near the top. There is a doughnut-shaped electromagnet built into the ceiling, and the iron collar swings back and forth inside the hole of the doughnut. When the pendulum cable reaches a particular point in its swing, it is detected by an electronic device and the magnet is turned on at just the right time to give the collar (and thus the cable and the bob) a little "kick" in the exact direction of its natural swing. This restores the energy lost during the swing and keeps the pendulum from stopping. It has no effect on the direction of the swing, and thus does not interfere with the demonstration that the earth is rotating.

https://www.si.edu/spotlight/foucault-pendulum#:~:text=Any%20pendulum%20consists%20of%20a%20cable%20or%20wire,one%20is%20hollow%20brass%2C%20weighing%20about%20240%20pounds%29.

Answer 1

the bobweight's mass minimizes the effect of energy loss due to air friction. The long pendulum arm allows the rotation of the pendulum's plane of motion to be easily seen by eye.

Answer 2

You have two major forms of loss from the pendulum: air resistance and hinge or bending losses.

Adding mass to the pendulum allows greater energy to be stored in the swing of a given angle, so the losses take longer to have a significant effect on the pendulum.

Adding length has two big benefits: it decreases the swing frequency and it allows for lower swing angles.

Air resistance is related to speed, and longer strings have lower speed. Bending and hinge losses will probably be proportional to angle changes over time, and longer strings will have lower angle changes.

Making a small, unpowered pendulum will be difficult. You can get a lot of air out of the vessel, but making a very-low loss hinge will be much trickier. Easiest is to just use a symmetric cable, like monofilament line or similar. If this is bending over a large range with a period less than a second, that's going to pull quite a bit of energy.

A lubricated mechanical hinge could probably be made with less bending loss in one plane, but I suspect making a hinge small, very-low loss, unpowered and that doesn't change the behavior as the swing angle changes would be difficult.