## 1.

The Correct Answer is (B) — Both studies are based on the idea that different compounds travel different distances through paper, based on their affinity for the solvent the paper is placed in. If the solvent is changed, the affinity of the compound for the solvent may change, which means the compound may travel a different distance through the paper. (A) and (C) are unverifiable with the passage, and therefore incorrect. (D) is incorrect because it states the results will be comparable, meaning the affinities of water and acetone must be identical. It then contradicts itself by stating that the affinities may not be the same.

## 2.

The Correct Answer is (H) — If a compound has the highest affinity for acetone, that means it traveled the farthest up the paper when acetone was the solvent. According to Table 1, that’s Compound 5, or (H). The Rf value of Compound 5 should also be the highest, and it is. (G) is incorrect because Compound 4 traveled the least distance, and therefore has the least affinity for acetone---if you chose this answer, you may have misinterpreted the relationship between distance travelled and affinity for acetone. Writing out the relationship clearly may help you avoid such mistakes: ↑DT = ↑A If you chose (F) or (J), you may not have read the correct rows of Table 1. Be sure make information easy to sort by using your Pencil on Paper strategy!

## 3.

The Correct Answer is (C) — The question tells you that a new compound, Compound 9, has a higher affinity for acetone than Compound 2, and a lower affinity for acetone than Compound 2. You should refer back to Table 1 and mark these rows. The question then asks what Compound 9’s Rf value would likely be. If it has a higher affinity than Compound 2, and a lower affinity than Compound 6, its Rf value will be between the Rf values of Compounds 2 and 6, which are 0.776 and 0.898, respectively. Therefore, the answer is (C). If you picked (B) or (D) you may have thought that a higher Rf value meant a lower affinity for acetone. If you did not mark the rows of the Table when you referred back to the passage, you may have chosen the wrong compounds. If you misread the question, then for questions that are long like this one, you should make a mark at each piece of given information, to make them all easier to organize.

## 4.

The Correct Answer is (H) — The passage introduction tells you that a solvent carries compounds through the paper. In both studies, the solvent used is acetone. If the acetone traveled farther up the paper, then it would have carried the compounds farther up the paper with it. The answer is (H), because the distances would therefore increase. (F) is the exact opposite of the correct answer. (G) is tempting, because it’s easy to imagine the Acetone Line in Figures 1 and 2 moving independently of all the dots, so be sure to verify any thought you have by referring back to other parts of the passage. (J) is incorrect because the movement of acetone is a variable that affects every compound in the same direction; therefore, you know that there must have been a change.

## 5.

The Correct Answer is (A) — According to the passage introduction, the distance traveled by a compound through paper is dependent on the compound’s affinity for the solvent. In order to separate different compounds most effectively, which means to increase the distance between them, a solvent should be used for which the compounds have very different affinities, or (A). If the compounds have very similar affinities for the solvent, they won’t separate that much, so (B) is incorrect. If the compounds have identical affinities for the solvent, they will not separate at all, so (C) is incorrect. If the compounds have unknown affinities for the solvent, then the student will not know how much they will separate, so this solvent is an ineffective choice, and (D) is incorrect.

## 6.

The Correct Answer is (F) — In order to determine what Mixture Z is composed of, you will need to look at more than Table 2---you will need to compare it to Table 1, and also put Pencil on Paper to keep track of your findings. According to Table 2, the first dot in Mixture Z, Z1 traveled 5.1 cm. This value is exactly the same as the distance Compound 7 traveled, according to Table 1. However, the acetone solvent traveled 9.8 cm in Study 1 and 9.7 cm in Study 2. Since these values are not identical, it is important to check the Rf values for both compounds as well. Their Rf values are also similar. Therefore, Mixture Z has Compound 7 in it, and you can eliminate any answer that does not, which is (G). Next, the second dot in Mixture Z, Z2, traveled 0.7 cm. This value is similar to the distance Compound 4 traveled, according to Table 1. Their Rf values are also similar. Therefore, Mixture Z has Compound 4 in it, and you can eliminate any answer that does not, which is (H) and (J). You’re left with (F) as the correct answer. You don’t have to compare the last row of Table 2 to Table 1, but you can see that Z3 is clearly Compound 1.

## 7.

The Correct Answer is (B) — Again, you should use Process of Elimination to solve this question. (A) is incorrect because the distances traveled by the acetone in both studies was not identical, and Rf is not applicable to acetone, either. (C) is incorrect because the density of acetone is irrelevant to this passage. (D) is incorrect because the Rf value indicates the affinity of a compound for a solvent, not anything about time or mixing. (B) is correct because the Rf value helps to compare both studies, as you can see in the explanation to #6, since the distances traveled by the acetone are not identical. The Rf value shows the relationship between the distances of the compound and solvent, rather than the absolute distance traveled by a compound, which would not be sufficient for determining a substance's affinity. The Rf value allows you to account for the possibility of different solvents traveling different distances.

## 8.

The Correct Answer is (H) — When you read the passage, you should have determined which scientist holds what viewpoint. Scientist 1 is “the genes view,” Scientist 2 is “the free radicals view,” Scientist 3 is “the telomeres view,” and Scientist 4 is “the hormones view.” (G) and (J) are immediately obvious as incorrect, since they have nothing to say about the shortening of nucleic acids. (F) is incorrect because Scientist 1 focuses on genes regulating other genes, not on the nucleic acids, which compose the genes, shortening. (H) is correct because telomeres are nucleic acids that shorten, and Scientist 3 says this is the cause of aging.

## 9.

The Correct Answer is (D) — All the scientists mention decreased protein production. Scientists 1 and 3 mention proteins most prominently, but don’t stop at (A), which is incorrect. Continue to search for the words “protein production” in the other three viewpoints. Scientist 2 says that free radicals mutate genes, which are no longer able to produce proteins. Therefore, (B) is incorrect. Scientist 3 states that when telomeres shorten, the genes they once protected are susceptible to damage, and no longer able to produce proteins, so (C) is incorrect. Scientist 4 notes that without hormones to initiate protein production, it slows and gradually stops. The correct answer is (D).

## 10.

The Correct Answer is (G) — If antioxidants inhibit reactive oxygen (which means they stop reactive oxygen from reacting so much), and also slow the aging process, then you can guess that reactive oxygen must cause aging. The only scientist who asserts this is Scientist 2, so (G) is correct. No other scientist mentions reactive oxygen, or even oxygen. Don’t apply any outside knowledge here. This is not material that you’re expected to know from your high school classes. Don’t rationalize, either. You may recognize the term “antioxidant” and want to associate it with other familiar terms, such as the hormones Scientist 4 discusses, but avoid this impulse. Instead, refer back to the passage.

## 11.

The Correct Answer is (A) — Scientist 1 claims that regulatory genes cause aging. Therefore, the correct answer must mention regulatory genes. The only answer that does so is (A). If regulatory genes cause aging, and regulatory genes, such as Indy, are inhibited, then the aging process would either stop or be drastically slowed, which is what (A) says. (B) and (D) mention hormones, which are related to Scientist 4’s viewpoint, and (C) talks about the shortening of nucleic acids, which is only relevant to Scientist 3, so they’re all incorrect.

## 12.

The Correct Answer is (H) — The question asks which scientists agree with the Error Hypothesis, which states that aging is caused by damage accumulated over time. Ignore the information about the Program Hypothesis; it’s meant to mislead you. Scientist 2 states that damage accumulates over time due to free radicals, and Scientist 3 states that damage accumulates over time due to the shortening of telomeres. Therefore, Scientists 2 and 3 both agree with the Error Hypothesis, so (F) and (G) cannot be correct because they exclude each other. (J) is incorrect because Scientist 4 does not discuss damage, but states that hormones gradually cease to be produced, and others signal biological processes to slow and stop, so Scientist 4 does not agree with the Error Hypothesis.

## 13.

The Correct Answer is (C) — Because Scientist 4 talks exclusively about hormones, look for an answer that mentions hormones. (A) and (B) are not relevant, since they refer to the views of Scientists 1 and 3 respectively. (D) is incorrect because it suggests that the immune system is more central to the aging process than hormones. Since Scientist 4 believes that hormones cause aging, she would be unlikely to agree with a claim that the immune system causes aging. (C) is correct because it incorporates the new viewpoint into Scientist 4’s viewpoint, without detracting from Scientist 4’s argument.

## 14.

The Correct Answer is (H) — This is a Knowledge question. It refers tangentially to the passage by mentioning “metabolism,” but the answer choices mention acronyms and words that are not in the passage. Therefore, you must rely on your science knowledge. DNA and RNA do not store energy, so (F) and (G) are incorrect. If you knew that DNA and RNA were made of nucleic acids, and were part of genes, then you could guess that these answers were incorrect based on the passage. (J) is incorrect because chlorophyll is a molecule used in plants to harvest light in photosynthesis. It does not store usable energy, but absorbs sunlight, which is immediately used to manufacture sugar. (H) is ATP, a molecule that your cells use to store energy. You can use our online material to familiarize yourself with important scientific concepts that could appear in ACT Knowledge questions.

## 15.

The Correct Answer is (D) — The question directs you to Figure 3, so ensure that you do not look at Figure 2, or you may choose (C), which is incorrect. If you refer back to Figure 3 and find the 30-year range with the greatest increase in mean July temperature, you would find that the greatest increase occurs between the years 1980 and 2010, which is (D). However, often on the Science Test, the range on the figure with the greatest increase will not be an answer option; in that case, your Prediction won’t help you, and you’ll have to map each answer choice onto the figure in order to compare them. (A) and (B) are incorrect because the slope of the line indicating temperature over time is not as steep in these ranges as it is between 1980 and 2010.

## 16.

The Correct Answer is (G) — This question directs you to part of Figure 2, but not the entire figure. Between the years 1860 and 1980, the greatest mean shrub height occurs in 1980, and it’s between 1.5 m and 2.0 m, or (G). If you chose (H), you may have looked at the whole figure, up to 2010. If you chose (J), you may have looked at Figure 3 by mistake.

## 17.

The Correct Answer is (B) — The passage states that the Alaskan moose has extended its range from the boreal regions, which are heavily forested, across the treeline and into the northern tundra. Therefore, the treeline must separate boreal and tundra, so (C) and (D) are incorrect. Also, the boreal was forested, and earlier, the passage noted that the tundra has some shrubs but no trees, so (B) is correct. (A) is the exact opposite of the correct answer. Putting Pencil on Paper and underlining new terms such as “boreal” or “tundra” may help with questions like these.

## 18.

The Correct Answer is (F) — The trend observed in Figure 3 is an increase in mean July temperature. The passage states that global warming has increased vegetation cover in the tundra, causing moose to migrate more northward. Therefore, if temperature continues to increase, then moose will continue to migrate northward. (F) reflects this trend, since according to Figure 1 the moose are not yet present in the North Slope. (G) is incorrect because, according to Figure 1, the moose reached the end of the Seward Peninsula around 1970, so their habitat is already extended there. (H) and (J) are incorrect because both of these regions are to the south of the moose’s current habitat, and increasing temperature means extending habitat, not shrinking (contracting) habitat.

## 19.

The Correct Answer is (C) — According to Figure 3, the mean July temperature in 2010 is slightly greater than 14°C. According to the question, the mean July temperature in 2016 was approximately the same, so around 14°C. In order to find the average foliage mass of S. richardsonii in 2016, refer back to Figure 4, which measures the average foliage mass of the two shrubs at different mean July temperatures. Find the 14°C mark on the x-axis of the second graph in the figure, the graph for Salix richardsonii. At this temperature, the average foliage mass is slightly less than 0.8 kg, which corresponds to (C) 0.78 kg. (A) and (B) represent average foliage masses of S. alaxensis, the first graph in Figure 4, around 14°C, instead of S. richardsonii. (D) is too low, and may result from a misreading of either Figure 3 or 4.

## 20.

The Correct Answer is (F) — According to Figure 4’s first graph, S. alaxensis increased in mass from slightly more than 0 kg to slightly less than 1.5 kg. According to Figure 4’s second graph, S. richardsonii increased in mass from slightly more than 0 kg to slightly less than 0.8 kg. Therefore, the first graph, of S. alaxensis, represents the greater change in average foliage mass. (F) is correct. (G) is a trap: simply because the line on the S. richardsonii graph is higher than the line on the S. alaxensis graph does not mean that S. richardsonii exhibited a greater change. Always ensure you examine the units of both axes to determine the magnitude of changes. (H) is incorrect because, although the graphs both have sigmoid curves with similar-looking slopes, the magnitude of the changes are not identical. (J) is incorrect, because both graphs clearly show an increase in mass.

## 21.

The Correct Answer is (B) — According to the passage introduction, the higher the surface tension, the more force will be required to break the surface of the solution. Greater force corresponds to greater mass, so the beaker for which the greatest mass was required contains the substance with the greatest surface tension. This is Beaker 2. According to the explanation of Activity 1, the second beaker was filled with salt water, so (B) is the correct answer. This question asks you to refer back to different parts of the passage, specifically to the explanation of Table 1, so if you did not refer back to the passage, or to the correct part of the passage, you may have chosen (A), (C), or (D). If you misinterpreted the relationship between mass and surface tension, which is M↑ = ST↑, you may have picked (D), thinking that acetone has the highest surface tension as it has the highest mass.

## 22.

The Correct Answer is (J) — As you know from the passage introduction and from #21, higher surface tension means greater mass required to move the needle. According to Figure 1, the mass required to move the needle decreases as temperature increases. Therefore, the students are correct, and you can eliminate the “No” answers, (F) and (G). (H) is incorrect because it’s the opposite of the correct answer: the mass required to move the needle is lower at higher temperatures, not higher.

## 23.

The Correct Answer is (B) — This question is a simple substitution, and asks you to perform algebra that you should have used in your various science classes. If force, F, is the same as m x g, then F = mg. None of the answer options have F in them, so you’re looking for the answer that takes the equation from Activity 3 and replaces F in it with mg. The answer is (B). (A) is an wrong rearrangement of the equation and is incorrect. (C) is the reciprocal of the correct equation, but there’s no reason to have flipped it upside-down, so it’s incorrect. (D) is just plain scrambled. Prediction can be a useful tool in questions like these if you are confident in your ability in manipulating simple equations.

## 24.

The Correct Answer is (F) — One of the 3 Ds that you should note, especially in Research Summary passages like this one, is differences. As you skimmed the passage, first looking at the tables and figures, you would’ve noticed that Table 1 measures four different solutions, and Figure 1 measures those same four solutions, but at different temperatures. Therefore, (F) is correct. (G) is the opposite of the correct answer, and mixes up Activities 1 and 2. (H) and (J) are both incorrect because surface tension was not calculated in either Activity 1 or Activity 2, but only in Activity 3.

## 25.

The Correct Answer is (C) — If students forgot to rinse the needle between Beaker 3 and Beaker 4, then some of the substance from Beaker 3 would still be on the needle when it was placed in Beaker 4. The substance in Beaker 3, glycerol, has a much greater surface tension than the substance in Beaker 4, acetone. Therefore, the students will measure a mass required to remove the needle from Beaker 4, and that measured mass will be greater than the actual mass required to remove the needle if the needle were not contaminated. If the measured mass is greater than the actual mass, then the actual mass (which is what the question asks for) is less than the measured mass, or (C). The phrasing of the question is confusing, and may have tempted you to choose (A) or (B). Always mark given information and the goal in long questions like this, so you won’t be confused. You may have chosen (D) if you thought there wouldn’t be much difference. You may be correct; there may not be that much difference between the measured mass and the actual mass. However, (D) states that these masses will be exactly the same, which is incorrect.

## 26.

The Correct Answer is (F) — According to the description of Activity 2, the students measured the mass required to move the needle from the four solutions at four separate temperature points. Even though the trend lines are continuous, there are really only discrete points at each of the temperatures for each of the substances. (F) is correct because if acetone boils at 56°C, then it will have a data point at 40°C but not at 60°C, at which point it is a gas. (G) is incorrect because the half-life of acetone is irrelevant to its temperature, and on the time scale of this experiment, 10 days is probably irrelevant to the surface tension as well. (H) is incorrect because the fact that acetone is an organic solvent is irrelevant to its surface tension and temperature. Distilled water, salt water, and glycerol are also organic solvents, and they have data points after 40°C. (J) is incorrect because acetone’s chemical formula does not indicate pertinent temperatures or surface tensions. Fun fact: there are also many isomers of acetone (molecules with different structures and the same chemical formula), such as cyclopropanol and methyl vinyl ether, and they all have different boiling points and surface tensions.

## 27.

The Correct Answer is (C) — According to Table 2, surface tension is measured in dyn/cm. Because Activity 3 states the formula for calculating surface tension, you know that a “dyn” is some kind of unit related to force. The larger the “dyn/cm,” therefore, the larger the surface tension. You can verify this fact by referring back to Table 1. Beaker 2, salt water, had the highest surface tension; in Table 2, Beaker 2 also has the highest dyn/cm value. The question states that acetic acid has a surface tension of 64.52 dyn/cm. According to Table 2, it would have the second-lowest surface tension. The lowest surface tension belongs to Beaker 4, which is acetone. If the substances are listed from lowest to highest surface tension, then acetone would come first, followed by acetic acid. The only answer to have this order is (C). (D) is tempting if you mix up the words “acetone” and “acetic acid,” which are very similar. (A) and (B) are tempting if you order the substances from highest to lowest surface tension, which is the opposite of what you’re asked to do.

## 28.

The Correct Answer is (H) — According to Table 1, the group with the highest reflectance is unshaved ants at a wavelength of 400 nm (5.9% reflectance). However, this is not an answer option. You must refer back to Table 1, map the groups onto the table, and use Process of Elimination to determine the correct answer. The group in (F) has a reflectance of 2.9%, but the group in (G) has a reflectance of 3.9%. Therefore, (F) is incorrect. The group in (H) has a reflectance of 5.5%, so (G) is incorrect. The group in (J) has a reflectance of 5.0%, so (H) remains correct. If you got this question wrong, make sure you are paying attention to the tables, labels and questions---it will get harder to focus closely and easier to miss things by the time you reach the Science Test, so you need to be careful.

## 29.

The Correct Answer is (D) — The dependent variable is usually the one that the scientists measure, as opposed to manipulate. Any change in the dependent variable depends on a change in another variable or set of variables, the independent variable(s). (A) is not measured in Study 1, so it isn’t a variable at all, and is incorrect. (B) is an independent variable because it is varied by the researchers, not because of any other variable. (C) is also an independent variable, for the same reason as (B). Changes in (B) and (C) are not caused by changes in anything else. (D) is the correct answer because depending on changes in wavelength and in amount of hair, reflectance will change. Reflectance is therefore the dependent variable.

## 30.

The Correct Answer is (G) — According to Table 1, the reflectance of shaved ants increases as wavelength increases. Since you can find the relationship between the reflectance and wavelength (↑W = ↑R), you can use Prediction to find the correct answer. Every 50 nm increase in wavelength corresponds to an increase in reflectance between 0.1% and 0.4%. Therefore, a 50 nm decrease in wavelength would result in a decrease between 0.1% and 0.4%. 2.2 – 0.1 = 2.1, and 2.2 – 0.4 = 1.8. The reflectance of shaved ants at 350 nm would be between 1.8% and 2.1%, which is (G). (F) is incorrect because it’s too extreme of a decrease; no value in the first column of Table 1 ever increases or decreases by more than 0.4%, and (F) is a decrease of 0.5%. (H) and (J) are incorrect because they indicate increases in the reflectance of shaved ants when wavelength decreases, which is the opposite of the trend shown in Table 1. You may have chosen (H) or (J) if you looked at the wrong column in Table 1.

## 31.

The Correct Answer is (C) — According to Figure 1, shaved ants exhibit a greater increase in internal temperature during a 90 second exposure to a solar simulator. Therefore, the researchers’ prediction is correct, and you can eliminate the “No” answers, (A) and (B). (D) is incorrect because the internal temperature of shaved ants rose more quickly than that of unshaved ants. Make sure to refer back to the Key and to the correct lines on Figure 1!

## 32.

The Correct Answer is (J) — One of the 3 Ds you should skim for, especially in Research Summary passages like this one, is Differences. Looking at Table 1 and Figure 1 is enough to tell you what Study 1 and Study 2 are measuring. Table 1 mentions wavelength and reflectance of both shaved and unshaved ants; Figure 1 mentions temperature and time for both shaved and unshaved ants. (F) and (G) are incorrect because they state that one of the studies doesn’t measure ants with different types of hair. What does “measuring ants” mean, anyway? (H) is the opposite of what the passage says, so it’s incorrect.

## 33.

The Correct Answer is (A) — According to Figure 1, the internal temperature of unshaved ants never reaches 30°C. In fact, it never reaches much higher than 28°C, so (C) and (D) are incorrect. (B) is incorrect because after 50 seconds, the temperature of shaved ants is around 29°C, not 30°C. (A) is correct because after 70 seconds, the temperature of shaved ants exceeds 30°C, and the ants would not survive.

## 34.

The Correct Answer is (F) — To solve this question, you first need to identify what type of ants are being tested based on Figure 1, and then find their reflectance at 450 nm based on Table 1. According to Figure 1, the group of ants that reaches an internal temperature of 30°C after 70 seconds is the shaved ants. The question then asks what the reflectance of these ants would be at 450 nm, so you must refer to Table 1. According to Table 1, shaved ants have a reflectance of 2.6% at 450 nm, so (F) is correct. You may have picked (J) if you thought you didn’t have information to determine the type of ants being tested; however, you can determine this based on Figure 1. (H) is incorrect, but you may have chosen it if you looked at the column for unshaved ants in Table 1, rather than at the column for shaved ants.

## 35.

The Correct Answer is (D) — According to Figure 1 and the passage introduction, objects moving in the northern hemisphere are deflected to the east of their original path. In Figure 1, this is clear for an object moving northward. This question presents an object moving southward, but it should still move to the east, which is to the right in this diagram. Point D is the only point to the right of the object’s original path, so (D) is correct. (A) is incorrect because it implies that the object does not move from its original position, but the question states that the object is traveling south. (B) is incorrect because it indicates that the object has moved to the west or its original path, which is what happens in the southern hemisphere, not in the northern hemisphere. You may have chosen (B) if you rationalized the diagram in Figure 1, and turned the arrows around in the wrong direction. (C) is incorrect because it implies that the Coriolis effect has no influence on the path of an object. You may have chosen (C) if you just wrote down what was presented on the diagram given in the question, but this arrow is a dotted line, which indicates original path, not actual path.

## 36.

The Correct Answer is (G) — According to Figure 2, as latitude increases, the rate of Earth’s rotation decreases. Recall that the Equator is at 0°N and the North Pole is at 90°N. If you got this backward, you may have chosen (F). (H) and (J) are both incorrect because the rate of Earth’s rotation is not the same at any two latitudes.

## 37.

The Correct Answer is (C) — This question presents a lot of given information in a short space: it asks for the inertial force of an object, and then tells you that the object has a mass of 7.5 x 105 kg, a velocity of 50 m/s, and a position of 90°N latitude. According to the Note on Figure 3, objects with a mass of 5 x 105 kg were measured at different velocities, and objects with different masses were measured at a velocity of 50 m/s. Since the speed of the object in the question is 50 m/s, and its mass is not 5 x 105 kg, you must refer to the objects with different masses only. They’re all traveling at 50 m/s. These are the solid black, dashed black, and dotted black lines. The gray lines are irrelevant to this question. Now that you’ve used velocity, one of the given pieces of information in the question, you can use another: mass. The object in the question has a mass of 7.5 x 105 kg. This value is not graphed on Figure 3, but two values around it are: 5 x $10^{5}$ kg and 1 x 106 kg. 7.5 x 105 kg falls exactly halfway between these values, so its inertial force will fall exactly halfway between the solid black line and the dashed black line. Now that you’ve used two pieces of given information from the question, velocity and mass, you can use the third: a latitude of 90°N. At this latitude, an object with mass 1 x 106 kg has an inertial force of slightly less than 175 N, and an object with mass 5 x 105 kg has an inertial force of slightly less than 125 N. Exactly halfway between these values is an inertial force of slightly less than 150 N, which is (C). You may have gotten (A) or (B) if you looked at a smaller latitude, a slower speed or lower mass instead of the given information. Considering a higher mass or faster moving object may have led you to get a high inertial force and pick (D). Because there are so many pieces of information in this question, ensure that you use your Pencil on Paper strategy to break up the question and the figure!

## 38.

The Correct Answer is (G) — An object with a uniform mass and velocity is simply an object whose mass and velocity do not change. This applies to every object in Figure 3, or every line. Every line in Figure 3 increases, so the inertial force acting on every object increases as the latitude increases northward. According to the passage, inertial force is what causes the Coriolis effect, so if the inertial force increases, then the Coriolis effect also increases when latitude increases northward. According to Figure 2, and as you know from #36, as latitude increases from the Equator to the North Pole (northward), the rate of Earth’s rotation decreases. Therefore, the rate of Earth’s rotation and the Coriolis effect have an inverse relationship: ↓ER = ↑CE. As the rate of Earth’s rotation increases, the Coriolis effect decreases, or (G). If you rationalized that a faster rotation meant more inertial force, you may have chosen (F), which is incorrect. You must always verify your guesses with information from the passage, particularly the figures. (H) is incorrect because neither of the figures exhibits an increase and then a decrease. (J) is incorrect because there is a clear trend.

## 39.

The Correct Answer is (A) — From your science classes, you should know that velocity is a measure of displacement, or change in position, divided by a change in time. If the speed of an object changes, then its velocity changes. Another way to think about this is that direction is important to velocity, so if direction changes, then velocity changes. The Coriolis effect changes the position and the direction of objects, so (A) is correct. (B) is tempting, but the weight of an object does not change when its position or direction do, so (B) is incorrect. (C) and (D) are incorrect because the Coriolis effect does not change mass or density.

## 40.

The Correct Answer is (J) — First, recall that for an object to be significantly affected by the Coriolis effect, it must experience a significant inertial force. To determine which of the objects would experience the most significant inertial force, you must look at Figure 3, and map each of the answer options onto it. Use chunking to break up the answers into their most important parts. Every object given in the answer options has a mass of 1 x 106 kg, but two have positions of 0°N and two have positions of 60°N, and two other pairs have velocities of 50 m/s and 100 m/s. You can therefore ignore mass, since all the objects have the same mass. According to Figure 3, all objects at 60°N experience a greater inertial force, and therefore Coriolis effect, than all objects at 0°N, so you can eliminate (F) and (G). The difference between (H) and (J) is the velocity of the objects, since both objects have the same mass and are at a position of 60°N. According to Figure 3, objects traveling 100 m/s always experience a greater inertial force, and therefore Coriolis effect, than objects traveling at 50 m/s (the dotted gray line is always higher than the dashed gray line). Therefore, (J) is correct.