What does a speed of 20 mph mean?
2 Answers
A speed of 20 mph is equivalent to 20 kilometers per hour. Here are the specific details: 1. Head unit: It resembles an electronic timer in appearance, featuring an LCD screen, buttons, metal contacts, etc., and is the most crucial part of the speedometer. 2. Mount, cable, and sensor: The mount is typically placed on the handlebar or stem of the bike to secure the head unit. Wired speedometers have a cable on the mount that connects it to the sensor installed on the front fork. Wireless speedometers do not have a cable; the sensor transmits data to the head unit via wireless signals. 3. Magnet: Installed on the spokes of the front wheel, its position corresponds to the sensor on the front fork. The head unit calculates speed and other data based on the time interval between the magnet passing the sensor twice in succession.
When we say '20 ma' while driving and chatting, it actually refers to a speed of around 20 kilometers per hour. This expression is quite common in southern China, mainly because people are accustomed to using a simpler way to convey speed. For example, when stuck in city traffic, being able to drive at '20 ma' is already considered smooth. However, it's important to note that 'ma' is not a standard unit—strictly speaking, kilometers per hour should be used. But for us veteran drivers who navigate city streets year-round, this phrasing feels particularly natural. Near kindergartens, we often remind ourselves to slow down to '20 ma' for safety, since even bicycles might overtake you at that speed. Mentioning '20 ma' on highways would be inappropriate—driving that slow would definitely get you honked at relentlessly by cars behind.
