Please answer this: I read this background article the other day: Liquid water is a fluid. The hydrogen bonds in liquid water constantly break and reform as the water molecules tumble past one another. As water cools, its molecular motion slows and the molecules move gradually closer to one another. The density of any liquid increases as its temperature decreases. For most liquids, this continues as the liquid freezes and the solid state is denser than the liquid state. However, water behaves differently. It actually reaches its highest density at about 4C. I am facing a new situation today: Steve and Chris sit down at a new cafe that just opened up in town after hearing rave reviews of it at work. They look at the menus trying to decide what to order when a waiter shows up and asks if they would like anything to drink. Steve says he would like a glass of water that has molecules far apart. Chris orders water with molecules closer together. The waiter looks at them with a rather confused look and asks them to please elaborate. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Who ordered colder water?
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Answer: Chris

Please answer this: I read this background article the other day: Look at the police car in Figure below . The sound waves from its siren travel outward in all directions. Because the car is racing forward (toward the right), the sound waves get bunched up in front of the car and spread out behind it. As the car approaches the person on the right (position B), the sound waves get closer and closer together. In other words, they have a higher frequency. This makes the siren sound higher in pitch. After the car speeds by the person on the left (position A), the sound waves get more and more spread out, so they have a lower frequency. This makes the siren sound lower in pitch. A change in the frequency of sound waves, relative to a stationary listener, when the source of the sound waves is moving is called the Doppler effect . You've probably experienced the Doppler effect yourself. The next time a vehicle with a siren races by, listen for the change in pitch. For an online animation of the Doppler effect, go to the URL below. I am facing a new situation today: John was sitting at point C near a railway track. Suddenly, he heard a train coming towards him from point A with constant sound of its horn. Eventually, it reached very close to him at point B. Then the train sped by him at point C where he was sitting, reaching point D after some time. Finally, it reached even farther from him at point E. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which point would have higher frequency, point A or point B?
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Answer: point B

Please answer this: I read this background article the other day: Huge amounts of chemicals, such as fertilizers and pesticides, are applied to farm fields (see Figure below ). Some of the chemicals are picked up by rainwater. Runoff then carries the chemicals to nearby rivers or lakes. Dissolved fertilizer causes too much growth of water plants and algae. This can lead to dead zones where nothing can live in lakes and at the mouths of rivers. Some of the chemicals can infiltrate into groundwater. The contaminated water comes up in water wells. If people drink the polluted water, they may get sick. I am facing a new situation today: Lucy and Sarah are two people who each own a lake that they enjoy spending time at. They have to take care of the lake though and make sure everything is healthy so that the lake can continue to thrive and people will want to visit it. Sarah says she heard a secret that if you dump fertilizer into your lake, the fish will grow twice as large. Sarah says she has just started doing it this past week and can't wait to see the results. Lucy is skeptical and waits to see what happens at Sarah's lake. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Is Lucy's lake more or less safe to drink than Sarah's?
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Answer:
more