Final answer:
In a Venturi flowmeter, the maximum velocity of air inside the tube can be determined using Bernoulli's equation, which relates the pressure gradient and the change in fluid velocity. If the area of the narrower section is 20% of the area of the inlet section, the velocity in the narrower section will be 1.41 times the velocity in the inlet section.
Step-by-step explanation:
A Venturi flowmeter is a device used to measure the flow rate of a fluid, such as air. In this case, we are considering air flow. The maximum velocity of air inside the tube can be determined using Bernoulli's equation, which relates the pressure gradient and the change in fluid velocity. According to Bernoulli's equation, the velocity is inversely proportional to the square root of the area. Since the area of the narrower section is 20% of the area of the inlet section, the velocity in the narrower section will be 1.41 times the velocity in the inlet section. Therefore, if there is a pressure gradient of 50 mmHg, the maximum velocity of air inside the tube will be 1.41 times the velocity corresponding to that pressure gradient.