ACT science practice test 48

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.


A simple pendulum consists of a mass (the pendulum bob) suspended by a string, as shown in Figure 8.6. In an experiment, the mass of the bob, the radius of the arc, and the release height (measured vertically from the bottom of the swing) were varied. Rather than measuring the speed at the bottom of the swing, energy analysis was used to predict the speed of the pendulum bob at the bottom of the swing. The results are shown in Table 8.4.

Figure 8.6

TABLE 8.4

A second experiment used the same scenario, but it included the measurement of the centripetal force and calculation of centripetal acceleration. Centripetal force is a real, unbalanced force pointed toward the center of an object's circular motion. Likewise, centripetal acceleration is defined as the component of acceleration directed toward the center. As a pendulum bob swings through the bottom of its arc, the string force dominates the gravitational force, thus providing the centripetal force that gives the pendulum bob its upward centripetal acceleration. The results are shown in Table 8.5.

TABLE 8.5

1. According to the data in Table 8.4, increasing the mass of the pendulum bob:

A. has no effect on the gravitational energy at the top of the swing.
B. decreases the gravitational energy at the top of the swing.
C. increases the radius of the arc.
D. has no effect on the speed at the bottom of the swing.

2. A 0.010-kg pendulum has an arc radius of 0.40 m. Using the data trends shown in Table 8.4, predict the kinetic energy at the bottom of the swing if it is released from a height of 0.35 m.

A. 0.025 J
B. 0.030 J
C. 0.035 J
D. 0.040 J

3. According to Table 8.4, when the release height doubles, the gravitational energy at the top of the swing:

A. doubles.
B. quadruples.
C. decreases to one-half its value.
D. decreases to one-fourth its value.

4. Which of the following conclusions about energy is supported by Table 8.4?

A. Kinetic energy at the bottom of the swing is directly proportional to speed.
B. Gravitational energy at the top of the swing is inversely proportional to release height.
C. Kinetic energy at the bottom of the swing is directly proportional to the radius of the arc.
D. Gravitational energy at the top of the swing equals kinetic energy at the bottom of the swing.

5. When the mass of the pendulum bob doubles, the kinetic energy at the bottom of the swing:

A. doubles.
B. quadruples.
C. decreases to one-half its value.
D. decreases to one-fourth its value.

6. When the pendulum bob's kinetic energy doubles, its speed:

A. doubles.
B. decreases to one-half its value.
C. increases by a factor of 1.4.
D. increases by a factor of 2.2.

7. According to Table 8.5, centripetal acceleration is

A. independent of mass.
B. directly proportional to mass.
C. inversely proportional to mass.
D. directly proportional to the radius of the arc.

8. When the radius of the arc doubles, the centripetal force:

A. doubles.
B. quadruples.
C. decreases to one-half its value.
D. decreases to one-fourth its value.

9. A car approaches a school zone with a speed limit of 20 miles per hour. Using the data trends shown in Table 8.4, how does the kinetic energy of a car speeding at 40 miles per hour compare to that of a car moving at the speed limit?

A. The speeding car's kinetic energy is one-half that of the other car.
B. The speeding car's kinetic energy is one-fourth that of the other car.
C. The speeding car's kinetic energy is twice that of the other car.
D. The speeding car's kinetic energy is four times that of the other car.

10. Using Table 8.5, predict the centripetal force on a 0.060-kg bob with a 0.40-m arc radius that is released from a height of 0.25 m.

A. 0.613 N
B. 0.736 N
C. 1.226 N
D. 9.800 N