What if two children push a swing at the same time? Would the swing go higher? Yes, together their force would be more. It is common for forces to be combined. Most objects on Earth have at least two forces acting on them. Do you know what one of them is? Of course, that force is gravity. How many forces do you have on you right now? Gravity pulls you down toward the center of Earth. Your legs exert a downward force. They hold you up against the pull of gravity. Consider the example in Figure 1.3. A book is resting on a table. Gravity pulls the book downward. It has a force of 20 newtons. At the same time, the table pushes the book upward. Its force is also 20 newtons. The table opposes the pull of gravity.

Question: "Which forces affect a book resting on a table?"

OPTIONS:
- no
- yes

Answer: "The force of gravity and the pull of the table"

Response: yes

Washington (CNN) -- The U.S. Food and Drug Administration announced Wednesday that laboratory tests on popular smoking devices known as electronic cigarettes have found they contain carcinogens and other toxic chemicals dangerous to humans. E-cigarettes are battery-operated and contain cartridges filled with nicotine and other chemicals. Known as "e-cigarettes," the devices are battery-operated and contain cartridges filled with nicotine and other chemicals, spiced with flavors such as chocolate, cola or bubble gum. While manufacturers tout e-cigarettes as a "healthy way" to smoke, federal health officials say the devices turn nicotine, which is highly addictive, and other chemicals into a vapor that is inhaled by the user. "The FDA is concerned about the safety of these products and how they are marketed to the public," said Dr. Margaret A. Hamburg, commissioner of the FDA. CNN contacted Florida-based Smoking Everywhere, one of the largest manufacturers of e-cigarettes, after the FDA announcement, and a spokeswoman said the company had no comment. Because e-cigarettes have not been submitted to the FDA for evaluation or approval, the agency had no way of knowing the levels of nicotine or the amounts or kinds of other chemicals that the various brands of these products deliver to the user. That is why the FDA began to test them. The FDA's Division of Pharmaceutical Analysis analyzed the ingredients in a small sample of cartridges from two leading brands of e-cigarettes. In releasing its information, the FDA did not identify the two companies, but said in one sample, diethylene glycol -- a chemical used in antifreeze that is toxic to humans -- was detected. Other samples detected carcinogens that are dangerous to those who smoke them, the FDA said. The FDA has been examining and seizing shipments of non-U.S.-made e-cigarettes at the U.S. border since summer 2008. To date, 50 shipments have been stopped. The products examined thus far meet the definition of a combination drug-device product under the Federal Food, Drug, and Cosmetic Act. "We know very little about these devices, said Dr. Jonathan Samet, director of the Institute for Global Health at the University of Southern California, "but to say they are healthy -- that's highly doubtful."

Question: "Describe some characteristics of e-cigarettes."

Response: "Cartridge filled with nicotene"
OPTIONS:
- no
- yes

A: yes

Problem: Greta ran to the corner with her older brother Tony. He had money for the ice cream truck in his pocket and she was very happy. The ice cream truck had been parked at the curb waiting for children for a very long time. The ice cream truck driver thought that no more children were coming to get ice cream so he started pulling away from the curb when they got to the corner. They yelled. They screamed, "Stop! Stop!" and jumped up and down on the side walk trying to get him to see them. The driver of the truck saw them, waved at them and smiled, pulled back to the curb and opened his truck up so that they could see everything that he had for sale. They were so excited. They saw some new treats. Tony wanted to try something new. He got an ice cream sundae with chocolate ice cream and nuts. He almost got a snow cone. Greta looked at everything that the ice cream truck had. She saw candy, ice cream cones, snow cones, and everything else. It all looked so good. But after looking at everything, she wanted to get an ice cream sandwich. She got the ice cream sandwich. She bit into it and smiled. It tasted so good. She felt so happy. Her brother, Tony, was happy too. He bit into his ice cream cone sundae and grinned. They walked home with their ice cream and told their mom about how close they came to not getting their ice cream at all. Their mom was happy that the truck had stopped for them. She said that they were very lucky to have gotten to the curb before the ice cream truck left.

Question: "What did Greta and Tony do to get the ice cream truck driver's attention?"

Answer: "They screamed, "Stop," and jumped up and down on the sidewalk"

OPTIONS:
- no
- yes
Answer: no

A flood occurs when a river overflows its banks. This might happen because of heavy rains. Floodplains In very flat regions, flood water may spread out on the surface of the land. It then slows down and drops its sediment. If a river floods often, a floodplain develops. A floodplain is an area where a thick layer of rich soil is left behind as the floodwater recedes. Thats why floodplains are usually good places for growing plants. They are very flat areas and they have very rich soils. The Nile River valley is a great example of a floodplain. Each year, the Nile River rises over its banks. This floodwater carries a lot of sediment. This sediment has been eroded off areas of land from upstream. This sediment is dropped as the water slows down after spreading across the land. What is left behind is a very rich soil. Thats why crops can be raised in the middle of a sandy desert. Natural Levees A flooding river often forms natural levees along its banks. A levee is a raised strip of sediments deposited close to the waters edge.

Question: "What forms the raised strip near the edge of a flooding river?"

OPTIONS:
- no
- yes

Answer: "Floodplain"

Response:
no