Unit 12 – Vector’s
Often, an object will have many forces acting on it simultaneously. Calculating the effect of each of the forces separately can be extremely complex and difficult. However, forces are vectors, and as such, any number of forces can be combined into a single net force vector (R) from which the object’s behavior can be determined.

Unit 13 – Cuba
The recorded history of Cuba began on October 12, 1492, when Christopher Columbus sighted the island during his first voyage of discovery and claimed it for Spain. Columbus named the island Isla Juana in reference to Prince Juan, the heir apparent. The island had been inhabited by Native American peoples known as the Taíno and Ciboney whose ancestors had come from South America and possibly North and Central America in a complex series of migrations at least several centuries before, and perhaps 6,000 to 8,000 years ago. The Taíno were farmers and the Ciboney were both farmers and hunter-gatherers; some have suggested that copper trade was significant and mainland artifacts have been found.

Unit 14 - Left and Right Brain Functions
Although the cerebrum [seribrem] is symmetrical in structure, with two lobes [loubz] emerging from the brain stem and matching motor and sensory areas in each, certain intellectual functions are restricted to one hemisphere [hemisfije]. A person’s dominant hemisphere is usually occupied with language and logical operations, while the other hemisphere controls emotion and artistic and spatial skills. In nearly all right-handed and many left-handed people, the left hemisphere is dominant.

Unit 15 - Hadrian’s Wall

Around AD [ej di:] 122, Roman Emperor Hadrian ordered the construction of a wall in northern Britain, then part of the Roman Empire, to keep out the unconquered Caledonians of Scotland. Built out of stone and turf [te:rf] and measuring [meżerinn] about 117 km (73 mi) in length, the wall linked a series of forts and watchtowers. The Romans rebuilt Hadrian’s Wall several times throughout [t/fruaut] the 200s and 300s and used it as a fortification until about 400.

Unit 16 - Chesapeake Bay Bridge-Tunnel
Chesapeake Bay features a piece of construction that may startle unprepared travelers. The 28.2 km (17.5 mi) crossing between Norfolk and Cape Charles, Virginia, begins as a bridge, but disappears into the water midway. A combination structure, the Chesapeake Bay Bridge-Tunnel combines two bridges with two tunnels that pass under major shipping channels.

Unit 17 - The Rolling Stones
The Rolling Stones are an English rock band, formed in 1962 in London when guitarist and harmonica player Brian Jones and pianist Ian Stewart joined vocalist Mick Jagger and guitarist Keith Richards. Bassist Bill Wyman and drummer Charlie Watts completed the early lineup. Although the members are over 60 the band is the most popular rock group in the world.

Unit 18 - Clipper Ship
A sharp, curved bow and an extremely large sail area made the clipper ship both swift and beautiful. Clipper ships enjoyed brief popularity in the middle of the 19th century, but were soon phased out of commercial trade by steamboats. The American clipper ship Antarctic, pictured here, was designed by architect Donald McKay, whose clippers were among the biggest and fastest ever built.