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Answer: In a rotating disk, when a particle moves from the center along a radius toward the edge, a force is generated that causes the disk’s rotational speed to decrease. Conversely, this will generate a force that causes the disk speed to increase or decrease. The magnitude of this force is directly related to the mass of the particle and its velocity. The first person to study such phenomena systematically was Coriolis; this force is also known as the Coriolis force. Replace the particle motion and trajectory in the aforementioned phenomenon with a pipe and the medium flowing within it, and limit the rotation in that phenomenon to back-and-forth rotation within a very small range. According to the Coriolis principle, when flowing outward from the center along the pipe, a force is generated that reduces the frequency of back-and-forth rotation. As it flows toward the center along the pipe, a force is generated that increases the frequency of back-and-forth rotation. The magnitude of this force is directly related to the density of the medium and the flow velocity. Create a pipe that causes the medium to flow downward first and then upward, and apply a force of fixed frequency that causes the section below the pipe to vibrate back and forth, thereby enabling the descending and ascending sections of the pipe to move in circular motions back and forth. When a medium flows through the pipe, due to the Coriolis force, a phase difference arises between the vibration frequencies of the descending and ascending sections of the pipe and the frequency that causes the pipe to vibrate. This phase difference is proportional to the density of the medium, the flow velocity, and the shape of the pipe (flow area). By detecting this phase difference, the mass flow rate can be determined directly. Flowmeters that operate on this principle are now all referred to as mass flowmeters. Flow meters that utilize the principle of heat exchange between fluids and solids: (Thermal type) A heating element is placed in the fluid, and as the fluid passes by, it absorbs heat from this element. When the temperature of the heating element remains constant, the temperatures of the fluid flowing past it before and after it will differ; this temperature difference is related to the mass of fluid flowing through the heating element, and by measuring this difference, the flow rate can be determined. Similarly, while maintaining a constant temperature difference, the flow rate can also be measured by detecting the temperature of the heat-generating element or the heating energy (current). Flowmeters that utilize this principle are generally called heat-type flowmeters. When the energy supplied to a heating element is constant, the temperature of the heating element is related to the mass of fluid flowing through it; meanwhile, the resistivity of the heating element varies with its temperature. By measuring the temperature of the heating element or its resistance value, it is also possible to determine the flow rate. Flowmeters that utilize this principle are generally called thermal conductivity flowmeters. Flow meters that operate on this principle include: hot-wire anemometers, Thomas flow meters, and boundary layer flow meters