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Integrated Physics and Chemistry TEKS Correlations (4) Science concepts. The student knows concepts of force and motion evident in everyday life. The student is expected to: (D)investigate and demonstrate mechanical advantage and efficiency of various machines such as levers, motors, wheels and axles, pulleys, and ramps. 84. For a simple machine to reduce the amount of force needed to do work, which of the following must increase? A. B. C. D. 85. Lubricants like motor oil and grease help increase a car’s efficiency by A. B. C. D. 86. The mass of the object that needs to be moved The distance the effort force moves The friction between the parts of the simple machine The number of parts in the simple machine reducing the amount of tire surface in contact with the ground increasing the energy content of the fuel reducing the friction between the moving parts increasing the amount of force the wheels apply If a machine is 46% efficient and can provide 85 joules of work output, approximately how much work must be put into the machine? A. B. C. D. 39 joules 54 joules 130 joules 180 joules These items (84-86) illustrate the many ways that efficiency of simple machines can be approached. The last item is simple calculation, whereas the first two items are more conceptual. Students may find the first two items much harder than the last. They can easily plug numbers into formulas, but rarely investigate machines to see that forces and distances change when applied to different machines or that there are things that can be done to a machine to make it more efficient. Charles A. Dana Center Science TEKS Toolkit www.sciencetekstoolkit.org