Problem: Given the question: Two researches studied adolescents during puberty. Tim studied males, while Dan studied females. Which researcher observed that growth in height is about 10 centimeters (almost 4 inches) per year in the average male? Hint: Another obvious change that occurs during puberty is rapid growth. This is called the adolescent growth spurt . In boys, it is controlled by testosterone. The rate of growth usually starts to increase relatively early in puberty. At its peak rate, growth in height is about 10 centimeters (almost 4 inches) per year in the average male. Growth generally remains rapid for several years. Growth and development of muscles occur toward the end of the growth spurt in height. Muscles may continue to develop and gain strength after growth in height is finished.
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The answer is:
Tim

Problem: Given the question: 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. Which point would have lower frequency, point D or point E? Hint: 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.
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The answer is:
point E

Problem: Given the question: A group of middle school students is measuring the temperature of various liquids for a chemistry lab using a mercury thermometer. They have a beaker of boiling water, a beaker of ice water, and a beaker of water at room temperature. If the mercury in the thermometer expanded did the students record a higher or lower temperature? Hint: A thermometer is a device used to measure temperature. It is placed in contact with an object and allowed to reach thermal equilibrium with the object (they will have the same temperature). The operation of a thermometer is based on some property, such as volume, that varies with temperature. The most common thermometers contain liquid mercury, or some other liquid, inside a sealed glass tube. The liquid expands and contracts faster than the glass tube. Therefore, when the temperature of the thermometer increases, the liquid volume expands faster than the glass volume, allowing the liquid to rise in the tube. The positions of the liquid in the tube can then be calibrated for accurate temperature readings. Other properties that change with temperature can also be used to make thermometers; liquid crystal colors and electrical conductivity change with temperature, and are also relatively common thermometers.
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The answer is:
higher