Answer the following question given this paragraph: Friction is the force that resists motion. In most beginning physics classes, friction is ignored. Concepts can be understood and calculations made assuming friction to be nonexistent. Whenever physics intersects with the real world, however, friction must be taken into account. Friction exists between two touching surfaces because even the smoothest looking surface is quite rough on a microscopic scale. Q: What type of force exists between two touching surfaces? Choices: - opposing - centrifugal - tension - friction A:
friction

Answer the following question given this paragraph: Q: The total energy assimilated by an ecosystem in a give period is known as what? Choices: - size primary production - median primary production - mean primary production - gross primary production A:
gross primary production

Answer the following question given this paragraph: Work is directly related to both the force applied to an object and the distance the object moves. It can be represented by the equation: Work = Force Distance. Q: Force times distance is the equation for what? Choices: - power - speed - gravity - work A:
work

Answer the following question given this paragraph: with only certain radii were allowed. Lines in the spectrum were due to transitions in which an electron moved from a higher-energy orbit with a larger radius to a lower-energy orbit with smaller radius. The orbit closest to the nucleus represented theground state of the atom and was most stable; orbits farther away were higher-energy excited states. Transitions from an excited state to a lower-energy state resulted in the emission of light with only a limited number of wavelengths. Bohr's model could not, however, explain the spectra of atoms heavier than hydrogen. Most light is polychromatic and contains light of many wavelengths. Light that has only a single wavelength is monochromatic and is produced by devices called lasers, which use transitions between two atomic energy levels to produce light in a very narrow range of wavelengths. Atoms can also absorb light of certain energies, resulting in a transition from the ground state or a lower-energy excited state to a higher-energy excited state. This produces an absorption spectrum, which has dark lines in the same position as the bright lines in the emission spectrum of an element. Q: What is light that has only a single wavelength called? Choices: - primary - fluorescent - spectroscopy - monochromatic A:
monochromatic