Problem: Surely, you have noticed the tall poles along the roadside. Do you know what is on top of those poles? Thats right, wires that carry electric current. These wires carry electric current to your home. But what is electric current? Electric current is actually the flow of electrons. You may recall, an electron is the outer-most particle in an atom. They have a negative charge. Electricity is the continuous flow of these particles. Electrons are able to move through wires. Their speed can even be measured. The SI unit for electric current (or speed) is the ampere (A). Ampere is often shortened to amp. Electric current may flow in just one direction, or it may keep reversing direction. Direct current (DC) flows in only one direction. Direct current is what is used in devices like flashlights. Alternating current (AC) flows in two directions. This is the type of current that flows into your home through wires.

Question: "What kind of particles are carried in the wires at the top of the tall poles along the roadside?"

Answer: "Electrical particles"

OPTIONS:
- no
- yes
Answer: yes

Problem: Early in chapter 5 we introduced, along with Khalid Sheikh Mohammed, two other men who became operational coordinators for al Qaeda: Khallad and Nashiri. As we explained, both were involved during 1998 and 1999 in preparing to attack a ship off the coast of Yemen with a boatload of explosives. They had originally targeted a commercial vessel, specifically an oil tanker, but Bin Laden urged them to look for a U.S.warship instead. In January 2000, their team had attempted to attack a warship in the port of Aden, but the attempt failed when the suicide boat sank. More than nine months later, on October 12,2000, al Qaeda operatives in a small boat laden with explosives attacked a U.S. Navy destroyer, the USS Cole. The blast ripped a hole in the side of the Cole, killing 17 members of the ship's crew and wounding at least 40. The plot, we now know, was a full-fledged al Qaeda operation, supervised directly by Bin Laden. He chose the target and location of the attack, selected the suicide operatives, and provided the money needed to purchase explosives and equipment. Nashiri was the field commander and managed the operation in Yemen. Khallad helped in Yemen until he was arrested in a case of mistaken identity and freed with Bin Laden's help, as we also mentioned earlier. Local al Qaeda coordinators included Jamal al Badawi and Fahd al Quso, who was supposed to film the attack from a nearby apartment. The two suicide operatives chosen were Hassan al Khamri and Ibrahim al Thawar, also known as Nibras. Nibras and Quso delivered money to Khallad in Bangkok during Khallad's January 2000 trip to Kuala Lumpur and Bangkok. In September 2000, Bin Laden reportedly told Nashiri that he wanted to replace Khamri and Nibras. Nashiri was angry and disagreed, telling others he would go to Afghanistan and explain to Bin Laden that the new operatives were already trained and ready to conduct the attack. Prior to departing, Nashiri gave Nibras and Khamri instructions to execute the attack on the next U.S.warship that entered the port of Aden.

Question: "On October 12, 2000 attacked a US navy destroyer, how many people on the destroyer were injured?"

Answer: "killed 40 and wounded at least 17"

OPTIONS:
- no
- yes
Answer: no

Problem: Magnets are able to place a force on certain materials. This force is called a magnetic force. The force a magnet exerts is a little different from the forces you may normally think about. You exert a force on a book when you lift it. You also exert a force on the pedals of your bicycle. In both those cases, those forces cause a change. The change you see in both these cases is called motion. Magnets, too, can produce change. They can produce motion just like you do. Unlike you, magnets do not have to touch something to exert a force. A magnetic force is exerted over a distance. Thats right, a magnet can push or pull certain items without ever touching them. Thats how the maglev train works. Do you know another type of force that does not require objects to touch? These forces are known as non-contact forces. Another type of non-contact force you may be familiar with is gravity. Gravity too can cause changes in motion. Gravity holds our moon in orbit without touching it.

Question: "How do magnets exert force?"

Answer: "A magnetic force is exerted over a distance"

OPTIONS:
- no
- yes
Answer:
yes