ACT science practice test 2

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.


Some physics students conducted experiments to study forces and springs. They used several identical springs attached to the bottom of a level platform, shown below in Figure 1.

Figure 1

The length of each spring was 0.30 m when there were no weights attached. The springs had identical spring constants. When weights were attached, the length of the springs increased as the force of the weights stretched the springs downward. The length the springs stretched was proportional to the force of the weight.

Experiment 1

The students attached different weights to two springs at once. When the springs stopped oscillating and came to a rest, the students measured their length. In Trial 1, a 10.0 N weight was attached to Spring A and Spring B, which were attached 0.25 m apart on the board. In Trial 2, a 15.0 N weight was attached to Spring A and Spring B. In Trial 3, a 20.0 N weight was attached to Spring A and Spring B. The effects of the weights on Springs A and B for the three trials are shown below in Figure 2.

Figure 2

Experiment 2

The students attached a 0.25 m board with a high friction surface to Spring B and Spring C (see Figure 3). The students then placed a 5.0 N weight at different locations along the board. Because of the high friction surface, the weights stayed in place when the board was at an angle.

Figure 3

In each of these 3 trials, a 5.0 N weight was placed at various distances along the board from the attachment with Spring B (see Figure 4). In Trial 4, the weight was placed so its center was 0.075 m along the board from the attachment with Spring B. In Trial 5, the weight was placed so its center was 0.125 m along the board from the attachment with Spring B. In Trial 6, the weight was placed so its center was 0.200 m along the board from the attachment with Spring B. The effects of the weight position on the lengths of Springs B and C for the 3 trials are also shown in Figure 4.

Figure 4

1. In a new study, suppose the students had placed a 10.0 N weight on Spring A only. Which of the following drawings most likely represents the results of this experiment?

A.
B.
C.
D.

2. In Experiment 2, as the distance between the 5.0 N weight and the attachment of the board to Spring B increased, the force exerted on Spring B:

F. increased only.
G. decreased only.
H. increased, then decreased.
J. decreased, then increased.

3. Which of the following statements is most likely the reason that the students used identical springs in Trials 1-3?

A. To ensure that the springs stretched similarly when a weight was attached.
B. To ensure that the springs did not share the weight evenly.
C. To compensate for the effects of oscillation on the results of the experiment.
D. To compensate for the weight of the board exerted on each of the springs.

4. Based on the results of Trials 1 and 5, the weight of the board used in Experiment 2 was:

F. 0 N.
G. 2.5 N.
H. 5.0 N.
J. 10.0 N.

5. In which of the following trials in Experiment 2, if any, was the force exerted by the weight and the board equally distributed between Springs B and C?

A. Trial 4
B. Trial 5
C. Trial 6
D. None of the trials

6. Assume that when a spring is stretched from its normal length, it stores the energy to return to its normal state as potential energy. Assume also that the greater the force of the weight stretching the spring, the more the spring will stretch. Was the potential energy stored by Spring C higher in Trial 5 or Trial 6?

F. In Trial 5, because the force of the weight on Spring C was greater in Trial 5.
G. In Trial 5, because the force of the weight on Spring C was less in Trial 5.
H. In Trial 6, because the force of the weight on Spring C was greater in Trial 6.
J. In Trial 6, because the force of the weight on Spring C was less in Trial 6.

Sodium chloride, or salt, is used to de-ice roads and sidewalks during the winter because it lowers the freezing point of water. Water with sodium chloride freezes at a lower temperature than water alone, so putting sodium chloride on icy sidewalks and roads can cause the ice to melt. Sodium chloride is highly effective as a de-icer and is given a de-icer proof of 100. Distilled water is ineffective as a de-icer and is given a de-icer proof of 0.

Different proportions of sodium chloride and distilled water were combined to create mixtures with de-icer proofs between 0 and 100.

Experiment 1

A 125-g cube of ice, frozen from distilled water, was submerged in 500-mL of each de-icing mixture listed in Table 1. After 300 seconds, the portion of the cube that had not been melted was removed and weighed. The de-icing rate was calculated by determining the weight of ice melted per second. By doing this, it was possible to determine de-icer proof for a solution based on the rate at which ice was melted.

Experiment 2

The addition of magnesium chloride to a de-icer changes its de-icer proof. Different amounts of magnesium chloride were added to 500-mL samples of sodium chloride. Each de-icing mixture was tested under the same conditions as Experiment 1 and the measured de-icing rate was used to calculate the de-icer proof. The results are shown in Figure 1.

Figure 1

Experiment 3

The temperature rating (TR) is the minimum de-icer proof of a de-icing solution for a de-icer to have any effect on ice. 125-g cubes of ice were submerged in 500-mL samples of De-icers A and B and the samples were then placed in freezers at different temperatures. Table 2 shows the de-icer proof determined for each de-icer at each freezer temperature and the known TR for that temperature.

7. Suppose a trial had been performed in Experiment 3 with a freezer temperature of -30°C. At this temperature, which of the following sets of proofs would most likely have been determined for De-icer A and De-icer B? De-icer A De-icer B

A. 68.8 59.7
B. 70.1 70.5
C. 75.5 61.8
D. 78.9 64.9

8. Based on

Table 1, if 1 mL distilled water were added to 4 mL sodium chloride, the proof of this mixture would be:

F. 4
G. 8
H. 40
J. 80

9. Based on Experiment 3, as temperature decreases, the minimum proof for a de-icer to be effective:

A. increases only.
B. decreases only.
C. increases, then decreases.
D. decreases, then increases.

10. Which of the following expressions is equal to the proof for each de-icer mixture listed in

Table 1?

F.
G.
H.
J.

11. Based on

Table 1 and Experiment 2, if 6 mL magnesium chloride were added to a mixture of 10 mL distilled water and 40 mL sodium chloride, the proof of the resulting de-icer would most likely be:

A. less than 60.
B. between 60 and 80.
C. between 80 and 112.
D. greater than 112.

12. Which of the 2 de-icers from Experiment 3 would be better to use to melt ice if the temperature were between -10°C and -75°C?

F. De-icer A, because its proof was lower than the TR at each temperature tested.
G. De-icer A, because its proof was higher than the TR at each temperature tested.
H. De-icer B, because its proof was lower than the TR at each temperature tested.
J. De-icer B, because its proof was higher than the TR at each temperature tested.