Why are drag-racing tires wide and smooth, whereas passenger-car tires are narrower and have tread? Are there frictional and/or safety considerations? Does this difference between the tires contradict the fact that friction is independent of surface area?
seniors in engineering are taught friction is proportional area
Drag-racers use slicks to maximize the surface area in contact with the road. Road tires are treaded to provide good traction in different weather condition, where racing tires are designed for dry weather conditions. The drag racing slicks are so large because of the tremendous amount of load they are put under. There is a lot of power under the hood of that car and the best way to translate it into speed is by using a large tire. This is why only the rear tires are so large. EDIT- It is also important to remember that when those tires speed up they go from wide and short to tall and skinny. Watch a video of a drag race's start carefully.
The Iron Age is the last principal period in the three-age system for classifying pre-historic societies, preceded by the Bronze Age. Its date and context varies depending on the country or geographical region. Classically, the Iron Age is taken to begin in the 12th century BC in the ancient Near East, ancient India (with the post-Rigvedic Vedic civilization), and ancient Greece (with the Greek Dark Ages). In other regions of Europe, it started much later. The Iron Age began in the 8th century BC in Central Europe and the 6th century BC in Northern Europe. Iron use, in smelting and forging for tools, appears in Nok civilization in West Africa by 1200 BC.[1] The Iron Age is usually taken to end in the Mediterranean with the onset of historical tradition during Hellenism and the Roman Empire, the onset of Buddhism and Jainism in India, the onset of Confucianism in China, or the early Middle Ages in the case of Northern Europe. The Iron Age roughly corresponds to the stage at which iron production was the most sophisticated form of metalworking. Iron's hardness, high melting point and the abundance of iron ore sources made iron more desirable and cheaper than bronze and contributed greatly to its adoption as the most commonly used metal. The arrival of iron use in various areas is listed below, broadly in chronological order. Because iron working was introduced directly to the Americas and Australasia by European colonization, there was never an Iron Age in either location.
