The Shape of a Football

Transcription

1 READTHEORY Name Date The Shape of a Football Although the shape of the football may seem strange, it is not the result of chance. In actuality, the decision to give the football its shape was deliberate; this shape is very important for both passing and carrying the ball. You see, a football is not a sphere (like a baseball, basketball, and soccer ball). Rather, a football is a special shape called a prolate spheroid. Instead of being round all over like a sphere, a prolate spheroid has two pointed ends. This shape makes a football much more aerodynamic than a rounder ball. Something that is aerodynamic can move easily through the air. Because a football is aerodynamic, it can fly through the air much faster than balls that are round. When a football is thrown very well, it flies in a spiral motion. This means that as the ball moves through the air, the tip of the ball stays pointing in one direction. The ball spins around and around like a drill. It does not flip over itself or wobble in the air. This spiral motion has what is called a gyroscopic effect on the ball. To understand what a gyroscopic effect is, think of a toy top. When the top is not spinning, it falls down to one side. When you spin the top, it stands up on its pointy end. This is the gyroscopic effect at work. The faster the top spins, the straighter it stands up. As the spinning slows down, the top starts to wobble and fall. A football works in a similar way. When a football is spinning very fast, the gyroscopic effect of the spin helps the ball travel smoothly in one direction. A spiral spin helps the ball to go exactly where the quarterback wants to throw it. A ball that wobbles or flips instead of spiraling will probably not end up where the quarterback wanted it to go. The shape of the football also makes it easier to carry than a round ball. When a player runs with the ball, opponents from the other team try to knock him down and make him drop the ball. This is called fumbling. The football s prolate spheroid shape is easier for a player to protect when he his running than a round ball. A good player will tuck the ball between his arm and his rib cage. This makes it less likely that an opponent will be able to cause a fumble while he is carrying it. The shape of a football may seem strange. After all, it's a lot different than the spheres used in other sports. But it is precisely this shape that makes football (and the football itself) so special. So the next time you are playing football and you make a great pass or running play, remember: it was partly thanks to the prolate spheroid! 1) In paragraph 1, we learn that "the decision to give the football its shape was deliberate." In other words, the decision to give the football its shape was A. strange B. very difficult C. made on purpose D. the result of chance

2 2) In this passage, we learn what it means to be "aerodynamic." Based on the information in the passage, which of the following is likely to be the most aerodynamic? A. a jet B. a pillow C. a tree D. a soccer ball 3) To better explain the gyroscopic effect, the author makes A. an argument, in which an idea is communicated that is intended to convince or persuade B. an analogy, in which a similarity between like features of two things is described C. a conclusion, in which a summary of the points and a statement of opinion or decisions reached D. a contradiction, in which a direct opposition between two things is compared 4) Which of the following sentences from paragraph 3 best describes the main idea of that paragraph? A. This is called fumbling. B. A good player will tuck the ball between his arm and his rib cage. C. When a player runs with the ball, opponents from the other team try to knock him down and get the ball out of his hands. D. The shape of the football also makes it easier to carry than a round ball. 5) How would American football be different if a sphere were used instead of a prolate spheroid? Explain your hypotheses.

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4 Answers and Explanations 1) C Core Standard: Craft and Structure deliberate (adjective): carefully weighed or considered; studied; intentional. In paragraph 1, the author writes, "Although the shape of the football may seem strange, it is not the result of chance." Here, we learn that the shape of the football is not the result of chance. The author continues, "In actuality, the decision to give the football its shape was deliberate; this shape is very important for both passing and carrying the ball." Here we learn that the shape of the football is deliberate. Using these two sentences, we can understand that something deliberate is not the result of chance. The author confirms this idea by stating further in the second sentence that the shape of the football is very important. So, something deliberate must be carefully weighed, considered, or intentional. In other words, the decision to give the football its shape was made on purpose. Therefore (C) is correct. The passage does not provide evidence to support choices (A), (B), or (D). Therefore they are incorrect. 2) A In the second half of paragraph 1, the author writes: Something that is aerodynamic can move easily through the air. Because a football is aerodynamic, it can fly through the air much faster than balls that are round. Based on this information, we can tell that aerodynamic things fly through the air easily. Out of all of the items presented in the choices, a jet is the item most likely to fly through the air easily. Therefore (A) is correct. Based on the above information, we can tell that aerodynamic things fly through the air easily. A pillow does not fly through the air easily. Therefore (B) is incorrect. Based on the above information, we can tell that aerodynamic things fly through the air easily. A tree does not fly through the air easily. Therefore (C) is incorrect. Based on the above information, we can tell that aerodynamic things fly through the air easily. The author also says: Because a football is aerodynamic, it can fly through the air much faster than balls that are round. A soccer ball is a round ball. It is not as aerodynamic as something like a jet, which was designed to fly through the air. Therefore (D) is incorrect. 3) B In paragraph 2, the author explains the gyroscopic effect. The author says that the spiral motion of a

5 football has a gyroscopic effect on the ball. To help readers understand what the gyroscopic effect is, the author tells readers to picture a toy top. The author explains how the toy top works. Then the author tells us that a football works "in a similar way." This last sentence is the critical, or most important, part. Here, a similarity between like features of two things is described. Given that this is the case, we can understand that the author makes an analogy to better explain the gyroscopic effect. Choice (B) is correct. The passage does not provide evidence to support choices (A), (C), or (D). Therefore they are incorrect. 4) D The main idea of a paragraph is often the first sentence of the paragraph. Because there are always exceptions to this rule, it is a good idea to read the entire paragraph before deciding that the first sentence contains the main idea. In paragraph 3, the author begins by stating: The shape of the football also makes it easier to carry than a round ball. The rest of the paragraph contains evidence that explains why the shape of the football makes it easy to carry. The author tells readers that when a player runs with the ball, opponents from the other team try to knock him down and make him drop the ball. This means that the player has to protect the ball. According to the author, The football s prolate spheroid shape is easier for a player to protect when he his running than a round ball. A good player will tuck the ball between his arm and his rib cage. The first sentence of this paragraph makes a claim (the shape of the ball makes it easy to carry) and the rest of the paragraph supports this claim with details. Because the paragraph is organized in this way, you can tell that the first sentence gives you the main idea of the paragraph. Therefore (D) is correct. The author explains what fumbling is in order to show readers why the shape of the ball is so important when it comes to running with the ball. Information about fumbling is evidence that the author uses to support his or her main claim (the shape of the ball makes it easy to carry). It is not the main idea itself. Therefore (A) is incorrect. The author explains how players protect the ball as they run so that readers can understand why the shape of the ball is so important. Information about how players carry the ball is evidence that the author uses to support his or her main claim (the shape of the ball makes it easy to carry). It is not the main idea itself. Therefore (B) is incorrect. The author explains why ball carriers have to protect the ball while they run with it in order to show readers why the shape of the ball is so important when it comes to running with the ball. This information is evidence that the author uses to support his or her main claim (the shape of the ball makes it easy to carry). It is not the main idea itself. Therefore (C) is incorrect.