ACT science practice test 54

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.


When the effect of air on a falling object is negligible and gravity is the only significant force on that object, the object is considered to be in freefall. A scientist can create a freefall scenario by removing all air from a chamber (thus creating a vacuum) and allowing an object to drop freely. When objects are not falling freely, air affects them in different ways, depending on variables such as speed, mass, and size. If objects are able to fall for enough time through the air, they will eventually reach terminal velocity, a point at which their velocity stops increasing. Table 10.1 and Figures 10.1 and 10.2 show the effect of air on falling balls of different mass and radius.

TABLE 10.1

Figure 10.1

Figure 10.2

1. According to Table 10.1, which of the following is a correct statement about the velocity of a 10-g freefalling ball?

A. The velocity is constant.
B. The velocity increases 9.8 m/s each second.
C. The velocity increases 4.9 m/s each second.
D. The velocity steadily decreases.

2. According to Table 10.1, which of the following is a correct statement about the distance a 10-g ball freefalls?

A. The distance increases constantly.
B. The distance increases 9.8 m each second.
C. The distance increases more each second compared to the previous second.
D. The distance increases 4.9 m each second.

3. According to Table 10.1, how much does the air drag force on the ball (10 g, 1 cm) increase during the fourth second of falling through air?

A. 0.000 N
B. 0.019 N
C. 0.061 N
D. 0.080 N

4. Using the trends in Table 10.1, predict the velocity of the 10-g ball at the instant it has fallen freely from rest for 14 seconds.

A. 9.8 m/s
B. 19.6 m/s
C. 118.0 m/s
D. 138.0 m/s

5. After comparing the data for the falling ball with and without air, which of the following is a correct statement about the effect of air on velocity?

A. The presence of air reduces the rate at which velocity increases.
B. The presence of air increases the rate at which velocity increases.
C. When air is not present, the velocity eventually stops increasing.
D. When air is present, the velocity eventually stops decreasing.

6. For the 10-g ball falling with air, Table 10.1 indicates that the force of air drag:

A. increases steadily with time.
B. plateaus initially and then decreases.
C. increases more each second compared to the previous second.
D. increases more rapidly early in the fall and eventually plateaus.

7. According to Figure 10.1, what is the effect of mass on the velocity of a falling object during the first five seconds as it falls through air?

A. Smaller masses lose speed more rapidly than larger masses.
B. Larger masses lose speed more rapidly than smaller masses.
C. Smaller masses gain speed more rapidly than larger masses.
D. Larger masses gain speed more rapidly than smaller masses.

8. As an object falls, the effect of air on its motion:

A. is more pronounced during the first few seconds.
B. is more pronounced later in the fall.
C. is minimal.
D. eventually dissipates.

9. When air is present, what is the effect of the radius of the ball on the velocity of a falling object during the first five seconds?

A. Smaller radii lose speed more rapidly than larger radii.
B. Larger radii lose speed more rapidly than smaller radii.
C. Smaller radii gain speed more rapidly than larger radii.
D. Larger radii gain speed more rapidly than smaller radii.

10. According to Figures 10.1 and 10.2, the terminal velocity of the 10-g ball with the 0.05-cm radius is most nearly:

A. 9.8 m/s.
B. 32 m/s.
C. 55 m/s.
D. 62 m/s.

11. In the absence of air drag, a ball with a larger radius:

A. has the same motion as one with a smaller radius.
B. reaches terminal velocity sooner than one with a smaller radius.
C. obtains a larger terminal velocity.
D. obtains a smaller terminal velocity.

12. According to Figures 10.1 and 10.2, the ball with less mass (but the same radius) falling through the air:

A. reaches terminal velocity later than a ball with more mass.
B. reaches terminal velocity within the first second it is dropped.
C. reaches terminal velocity sooner than a ball with more mass.
D. has the same terminal velocity as the ball with more mass.

13. Suppose one skydiver jumps out of an airplane feet first toward the ground. Her identical twin sister jumps out at the same time with her arms and legs extended and her stomach parallel to the ground. According to the passage, what can you infer about their subsequent motion?

A. The feet-first twin will reach terminal velocity first.
B. The belly-first twin will reach terminal velocity first.
C. Both twins will reach terminal velocity at the same time.
D. The belly-first twin will obtain a greater terminal velocity.

14. A table-tennis ball with a mass of 3 g is dropped side by side with an identical-sized wooden ball with a mass of 30 g. Based on the information provided, what can you conclude if the balls fall in a vacuum (no air)?

A. The 30-g ball will hit the ground first.
B. The 3-g ball will hit the ground first.
C. Both balls will hit the ground at the same time.
D. The 3-g ball will speed up more at first.

15. A table-tennis ball with a mass of 3 g is dropped side by side with an identical-sized wooden ball with a mass of 30 g. If both balls are dropped from rest and fall through the air, what can you conclude?

A. The 30-g ball will hit the ground first.
B. The 3-g ball will hit the ground first.
C. Both balls will hit the ground at the same time.
D. The 3-g ball will speed up more at first.

16. According to the data trends illustrated in the passage, a ball dropped in a vacuum without air will:

A. eventually reach terminal velocity as it's falling.
B. speed up at a steady rate as long as it has room to drop.
C. speed up at greater rate if it's more massive.
D. speed up at lesser rate if it's more massive.