问题
填空题
密度计是测量_______的仪器，在图中，同一支密度计分别放在甲、乙两种液体中均静止不动，则密度计在这两种液体中受到的浮力F甲_______F乙，两种液体密度ρ甲______ρ乙。
答案
液体密度、=、<
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密度计是测量_______的仪器，在图中，同一支密度计分别放在甲、乙两种液体中均静止不动，则密度计在这两种液体中受到的浮力F甲_______F乙，两种液体密度ρ甲______ρ乙。
液体密度、=、<
People who are outdoors in cold weather should avoid actions like suddenly lifting a heavy basket full of snow. Even walking through heavy, wet snow can strain a person’s heart. Many people aren’t conditioned to the physical stress of outdoor activities and don’t know the dangers of being outdoors in cold weather. Those who like winter sports can suffer accidental hypothermia if they don’t make certain preparations. Hypothermia means the body temperature has fallen below normal. It occurs when your body can’t produce enough energy to keep the internal (内部的) body temperature warm enough. It can kill you. Heart failure causes most deaths in hypothermia. Children, the elderly and those with heart disease are at special risk. As people age, their ability to keep a normal internal body temperature often decreases. Elderly people can suffer hypothermia without knowing they’re in danger because they can’t notice the cold conditions as quickly as the young. Besides cold temperatures, high winds, snow and rain can also steal body heat. Wind is especially dangerous because it removes the layer of heated air from around your body. At 30 degrees Fahrenheit in a 20-mile-per-hour wind, the cooling effect is equal to calm air at four degrees. Similarly dampness (湿气) causes the body to lose heat faster than it would at the same temperature in drier conditions. To keep warm, wear more clothes. This traps air between layers. Also, wear a hat or head scarf. Much of your body’s heat can be lost through your head. Keep your hands and feet warm, too, as they tend to lose heat rapidly. Don’t drink alcohol before going outdoors or when outside. Alcohol makes you feel warm at first because blood vessels in the skin expand. But heat is then drawn away from the body’s important organs. 1. The underlined word “strain” in Paragraph 1 means ________. A. injure B. warm C. control D. burn 2. What is implied in the passage about hypothermia?
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