Ademographic transition model is used to describe the relationship between the population of an area and the
economy. as early as the 1920's, it was observed that it was observed that in countries with high standards of living, the
population grew at a slow rate, while in countries with low standards of living, the population grew more rapidly. this
observation resulted in the concept of demographic transition, which is a series of stages that a country goes through while
changing from a non-industrial to an industrial country.
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the decline in death rate and birth rate that occurs during the demographic transition may transform the age structure within a
country. consider the population pyramids seen here. explain how you can tell that stage 1 above is typical of the hunting.
gathering societies previously viewed in the demographic transition model.
a)
there is a declining birth rate and death rate.
there is a high birth and death rate and short life expectancy.
there is a high birth rate and low death rate, with little population growth
the death rate is high for the younger segment of the population so few
reach old age.

Which of the following changes to a pipe would increase the conductance by a factor of 12? 1.quadrupling the length and tripling the radius.2.reducing the length by a factor of and doubling the radius.3.tripling the length and reducing the radius by a factor of .4.reducing the length but a factor of and doubling the radius.

Which type of wave can travel without a medium

19. explain why a magnet from your refrigerator could not be used to lift something as heavy as a car. (chapter 7 – pages 202-203) 20. can a magnet ever have a single pole? explain your answer. (chapter 7 – page 208) 21. what happens to the wavelength of a wave if the frequency is increased? (chapter 9 – pages 280-281) 22. an ocean wave has a wavelength of 10 m and a frequency of 4.0 hz. what is the velocity of the wave? show the appropriate equation from your book and show your work with units. (chapter 9 – page 282) 23. as you sit outside, the sound of a siren becomes lower in pitch. is the emergency vehicle moving away from or towards you? explain how you know. (chapter 10 – page 315-316) 24. why are two astronauts in space unable to hear one another? (chapter 10 – page 307) 25. explain in at least 3 sentences how electromagnetic waves form. (chapter 11 – page 338-339) 26. using the chart on page 345 in your textbook, what are the three types of electromagnetic wave with wavelengths shorter than those of visible light. give an example of each. (chapter 11 – pages 345-351) 27. explain why a leaf usually appears to be green, but a rose typically appears red. (chapter 12 – page 373) 28. what is the difference in light that is refracted compared to light that is reflected? think in terms of speed of light as well as what happens to light waves when they interact with a medium. (chapter 12 – pages 369-370) 29. how are concave and convex lenses different? (chapter 13 – page 408-410) 30. what type of mirror is used in rearview mirrors in cars? why is it important that these mirrors have the warning, “objects in mirror are closer than they appear.”? (chapter 13 – page 405)