ACT science practice test 81

Directions: Each passage is followed by several questions. After reading a passage, choose the best answer to each question and fill in the corresponding oval on your answer document. You may refer to the passages as often as necessary.

You are NOT permitted to use a calculator on this test.


Two experiments were performed to study Newton’s laws of motion using air track gliders. The friction between the gliders and the air track is nearly zero. Each glider has a spring attached on each end.

Experiment 1

Two identical gliders were placed on an air track as shown in Figure 1. The gliders’ springs were then compressed completely together along with the gliders and released. When the gliders were pushed apart by their springs, the data in Table 1 was recorded. The zero position was recorded as the far-left point where Glider 1 is shown in Figure 1.

Table 1

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Figure 1

Experiment 2

The same experiment was performed but Glider 3 was a double-weight glider in the first trial. In the second trial, Glider 4, a triple-weight glider, was tested.

Table 2

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The velocity for each trial was calculated and the ratio of Glider 1 to the other glider was graphed and shown in Figure 2.

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Figure 2

1. Suppose another trial was run with Glider 1 and a Glider 4 that weighs 4 times Glider 1. The ratio of the velocities would be closest to what number?

A. 1
B. 2
C. 3
D. 4

2. In Experiment 1, how many times a second did the experimenters record the position of the gliders?

F. Once per second
G. Twice per second
H. Three times per second
J. Four times per second

3. Based on Tables 1 and 2, how did the total distance traveled by both gliders vary against the weight of the gliders?

Total Distance----Total Weight

A. Decreased Increased
B. Increased Decreased
C. Increased Increased
D. Unchanged Increased

4. Based on Table 2, how far had Glider 4 traveled after 1.5 seconds?

F. .02 m
G. .06 m
H. .80 m
J. .86 m

5. What distance was separating the gliders before they were released in each experiment?

A. 0 m
B. .02 m
C. .05 m
D. .08 m

Since carbon is essential to life on Earth, understanding the global carbon cycle can provide valuable information. Through the process of photosynthesis, plants on land or algae living in water convert carbon dioxide into organic products. Through the process of respiration, organisms convert these organic compounds into energy and release carbon dioxide. Figure 1 displays the global carbon cycle.

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Figure 1

A significant amount of carbon is released through the burning of fossil fuels. Some of this carbon is stored in the atmosphere, while a significant portion is stored in ocean waters and sediments. Carbon in the ocean is described as dissolved inorganic carbon, particulate inorganic carbon, particulate organic carbon (POC), and dissolved organic carbon (DOC). Particulates are defined as those larger than 0.2 micrometers, whereas dissolved matter is that smaller than 0.2 micrometers (see Figure 2).

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Figure 2

Chromophoric dissolved organic matter (CDOM) is the colored portion of DOC. It is colored because it intensely absorbs violet and blue light. Figure 3 displays DOC and CDOM absorption in the tropical North Atlantic Ocean.

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Figure 3

6. Based on Figure 1, how much carbon is transmitted from the ocean to the atmosphere?

F. 91.9 Pg C/yr
G. 90.6 Pg C/yr
H. 918 Pg C/yr
J. 700 Pg C/yr

7. According to Figure 2, which of the following is NOT considered a dissolved carbon?

A. Proteins
B. Salts
C. Algae
D. Viruses

8. Based on Figure 3, which of the following statements best describes the relationship between ocean depth and amount of DOC?

F. As the ocean depth increased, the amount of DOC remained fairly constant, then decreased steadily, then began to increase again.
G. As the ocean depth increased, the amount of DOC steadily decreased.
H. As the ocean depth increased, the amount of DOC remained fairly constant, then decreased steadily, then became fairly constant again.
J. As the ocean depth increased, the amount of DOC steadily increased.

9. Suppose a fragment of organic carbon was found in the ocean and measured approximately 0.01 micrometers. It would mostly likely be featured in Figure 2 by which of the following?

A. Gases
B. Protozoa
C. Bacteria
D. Small polymers

10. At an ocean depth of 100 m, there is approximately how much CDOM, according to Figure 3?

F. 0.25
G. 0.12
H. 40
J. 70

11. Which of the following fragments, if found in the ocean, would be described as dissolved inorganic carbon?

A. Bacteria
B. Protozoa
C. Viruses
D. Polymers