An archer using a simple bow exerts a force of 180 N to draw back the bow string 0.50 m.
(a) What is the average work done by the archer in preparing to launch her arrow? (Compute the average work as you would any average quantity: average work 5 12 [final work – initial work].)
(b) If all the work is converted into the kinetic energy of the arrow upon its release, what is the arrow’s speed as it leaves the bow? Assume the mass of the arrow is 0.021 kg and ignore any kinetic energy in the bow as it relaxes to its original shape.
(c) If the arrow is shot straight up, what is the maximum height achieved by the arrow? Ignore any effects due to air resistance in making your assessment.
One sometimes hears the expression, “It was like shooting fish in a barrel!” This usually is taken to mean that the task, whatever it was, was easy to complete. But is it really easy to shoot fish in a barrel? Only if you know some optics! Suppose you’re in a boat and spy a large fish a few meters away. If you want to shoot the fish, how should you aim? Above the image of the fish? Below it? Directly at the image? Explain your choice. (You may assume that the path of the projectile you fire will not be deviated from a straight line upon entering the water, unlike light.)
Concept maps can be used as substitutes for traditional note taking when you read articles in magazines and newspapers. This question illustrates the point. Chapter 7 describes a number of interesting devices based on the concepts of electric charge and force, electric currents, and electric circuits. Some of these applications of the principles of electricity include semiconductor devices, electrostatic precipitators, superconducting devices (such as MRI machines), transformers, and so on. Using the Internet or resources available at your library, locate and read an article on one of these devices.
After reading the article, look back through it and circle or identify the key concepts in it. Then, using only the concepts you have identified, try to construct a concept map that accurately relates the major ideas or issues raised in the article. After completing the map, reflect for a moment on the degree of difficulty of this exercise. Are some major “concepts” missing from the article that you, the reader, had to “add,” based on your own knowledge, to make sense of the article and, hence, your map? What does this suggest to you about the quality or level of sophistication of the piece you read?