S O LV E D P R O B L E M 8 In an experiment, a robot is programmed to move at a constant speed. The time it takes to travel 20 m at different speeds is measured. Look at the results: v (m/s) 20 16 10 5 4 2 t (s) 1.00 1.25 2.00 4.00 5.00 10.00 a) Draw the graph. b) What law can be concluded from this study? Check it is correct. c) W hat is the speed of the robot if it takes 8 s to travel 20 m? a) b) Draw the line of best fit. I t is a rectangular hyperbolic curve. This indicates that they are inversely proportional quantities. The law: The speed of the robot is inversely proportional to the time it moves. Mathematical formula: v ? t = k. Check: for all values, v ? t = 20 m. c) Interpolate for t = 8 s. v ? 8 s = 20 m; v = 20 m / 8 s= 2.5 m/s v (m/s) t (s) 0 5 10 15 0 5 10 15 20 43 Look at the results of weighing different amounts of oil: Voil (mL) 100 150 200 250 m (g) 90 110 130 150 a) Draw the graph. What is the relationship between the two quantities? b) Read the graph. Find what the scales would show for these amounts of oil: 25 mL 0 mL. What does this value mean? Technological applications 44 Read this article and answer the questions. Female astronomers: the thick glass cei ling for women who look at the universe In her book The Glass Universe (Vi k ing , 2016), the Amer ican w r iter and ex pla iner of scienti f ic topics Dava Sobel ta l k s about how the Har vard Col lege Obser vator y began to employ women as "computers" in the mid-19th centur y. They recorded the obser vations that the men made w ith the telescope. The histor y of this obser vator y is unique because in 1893 it employed a lmost an equa l number of men and women: 42 . 5 % of the assistants were women. […] A lthoug h many of the lead ing women a re not famous now, they d id an impor tant job. Th is is a fact that they k new. They helped to: · ident i f y the nat u re of the sta rs · establ ish categor ies · measu re d istances in space. […] Accord ing to the w r iter, men were a lso ava i lable to do that work , but the d i rector chose women. "Maybe he thoug ht they were more pat ient and ca ref u l w ith the deta i ls. But he a lso k new that he cou ld pay them lower wa ges ," says Sobel . […] Henrietta Leav itt was the f irst person to notice that there was a relationship between the ma x imum brightness of stars and the period when their brightness varied. This relationship prov ided a tool to measure distances in space. Edw in Hubble used this tool to discover that the universe is expanding. […] elasombrario.publico.es 19th May 2019 (Adapted) a) Do you think calculations are very important in scientific work? Why? b) When Leavitt analysed her data, she found a way to calculate the distance to the stars. Do you think an electronic computer could have done all of Leavitt's work? Explain why. c) Leavitt's studies formed the basis of the big bang theory. Why is the big bang called a theory? d) Before the film Hidden Figures was released, almost nobody knew that women had been working in such important jobs at NASA for decades. Why do you think that happened? Does it seem fair to you? 1 31
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