Problem: Although Bin Laden, Atef, and KSM initially contemplated using established al Qaeda members to execute the planes operation, the late 1999 arrival in Kandahar of four aspiring jihadists from Germany suddenly presented a more attractive alternative. The Hamburg group shared the anti-U.S. fervor of the other candidates for the operation, but added the enormous advantages of fluency in English and familiarity with life in the West, based on years that each member of the group had spent living in Germany. Not surprisingly, Mohamed Atta, Ramzi Binalshibh, Marwan al Shehhi, and Ziad Jarrah would all become key players in the 9/11 conspiracy. Mohamed Atta was born on September 1, 1968, in Kafr el Sheikh, Egypt, to a middle-class family headed by his father, an attorney. After graduating from Cairo University with a degree in architectural engineering in 1990, Atta worked as an urban planner in Cairo for a couple of years. In the fall of 1991, he asked a German family he had met in Cairo to help him continue his education in Germany. They suggested he come to Hamburg and invited him to live with them there, at least initially. After completing a course in German, Atta traveled to Germany for the first time in July 1992. He resided briefly in Stuttgart and then, in the fall of 1992, moved to Hamburg to live with his host family. After enrolling at the University of Hamburg, he promptly transferred into the city engineering and planning course at the Technical University of Hamburg-Harburg, where he would remain registered as a student until the fall of 1999. He appears to have applied himself fairly seriously to his studies (at least in comparison to his jihadist friends) and actually received his degree shortly before traveling to Afghanistan. In school, Atta came across as very intelligent and reasonably pleasant, with an excellent command of the German language. When Atta arrived in Germany, he appeared religious, but not fanatically so. This would change, especially as his tendency to assert leadership became increasingly pronounced. According to Binalshibh, as early as 1995 Atta sought to organize a Muslim student association in Hamburg. In the fall of 1997, he joined a working group at the Quds mosque in Hamburg, a group designed to bridge the gap between Muslims and Christians. Atta proved a poor bridge, however, because of his abrasive and increasingly dogmatic personality. But among those who shared his beliefs, Atta stood out as a decisionmaker.

Question: "What took Atta to Germany and how long was he there?"

Answer: "In 1992 we went to live with a host family and attend University of Hamburg until 1999, a total of 7 years"

OPTIONS:
- no
- yes
Answer: yes

Problem: Rough surfaces create more friction than smooth surfaces. Thats why cars have tires. Its also why we use rubber mats in areas that might get wet. In your bathtub, you may even use No-Slip tape. No-slip is another way of saying the items has a lot of friction. In Figure 1.9, the blades of the skates are very smooth. Thats why you cant slide across ice with shoes. The soles of your shoes are much rougher than skates. The rougher surface of shoes causes more friction and slows you down. Heavier objects also have more friction. A heavy object presses down with more force. The surfaces are held together more tightly. This makes the surfaces harder to slide past each other. Did you ever try to push something heavy across the floor? Heavy objects are much harder to push than light objects.

Question: "Do ice skates provide much friction?"

Answer: "Yes"

OPTIONS:
- no
- yes
Answer: no

Problem: Heat supplies the energy that causes motion. The deeper you go into toward the Earths core, the hotter it gets. At the core it is really hot. All that heat tries to rise toward the surface. In the Mantle, the rock is partially melted and is able to move. As it is heated, the material in the mantle moves toward the surface. As the mantle material rises, it cools. When it reaches the Earths crust, it is mostly stopped. A little of the material can break through the surface, but not all. Instead, it begins to move horizontally. The mantle material moves horizontally away from a mid-ocean ridge crest. Toward the surface, the mantle material starts to cool. As it cools it sinks back down into the mantle. These areas are where deep sea trench occur. The material sinks back down to the core. The system operates like a giant conveyor belt. The motion due to heating and cooling is called convection.

Question: "What can the motion of convection be compared to?"

Answer: "A big mantle"

OPTIONS:
- no
- yes
Answer:
no