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: "How many directions does a current flow in a flashlight?"

Answer: "2"
Answer: no

Problem: "What goes up must come down." You have probably heard that statement before. At one time this statement was true, but no longer. Since the 1960s, we have sent many spacecraft into space. Some are still traveling away from Earth. So it is possible to overcome gravity. Do you need a giant rocket to overcome gravity? No, you actually overcome gravity every day. Think about when you climb a set of stairs. When you do, you are overcoming gravity. What if you jump on a trampoline? You are overcoming gravity for a few seconds. Everyone can overcome gravity. You just need to apply a force larger than gravity. Think about that the next time you jump into the air. You are overcoming gravity for a brief second. Enjoy it while it lasts. Eventually, gravity will win the battle.

Question: "Are you overcoming gravity for an hour when you jump on a trampoline?"

Answer: "No"
Answer: yes

Problem: At 8:38, Ong told Gonzalez that the plane was flying erratically again. Around this time Sweeney told Woodward that the hijackers were Middle Easterners, naming three of their seat numbers. One spoke very little English and one spoke excellent English. The hijackers had gained entry to the cockpit, and she did not know how. The aircraft was in a rapid descent. At 8:41, Sweeney told Woodward that passengers in coach were under the impression that there was a routine medical emergency in first class. Other flight attendants were busy at duties such as getting medical supplies while Ong and Sweeney were reporting the events. At 8:41, in American's operations center, a colleague told Marquis that the air traffic controllers declared Flight 11 a hijacking and "think he's [American 11] headed toward Kennedy [airport in New York City]. They're moving everybody out of the way. They seem to have him on a primary radar. They seem to think that he is descending." At 8:44, Gonzalez reported losing phone contact with Ong. About this same time Sweeney reported to Woodward, "Something is wrong. We are in a rapid descent . we are all over the place." Woodward asked Sweeney to look out the window to see if she could determine where they were.

Question: "Why did the passengers in coach think the airplane was in rapid descent?"

Answer: "They thought they were descending"
Answer:
no