NES Profile: Earth and Space Science (307)

A researcher collects water samples from a pond. The dissolved oxygen content of the samples will be measured later in a laboratory to determine the dissolved oxygen content of the pond's water. Which of the following procedural steps taken by the researcher will help ensure that the samples accurately reflect the dissolved oxygen content of the pond water?

1. collecting samples from the surface in the same near-shore location and keeping the sample jars cool until testing is done
2. filling sample jars to the top with water collected from several recorded depths and locations and then rapidly sealing them for storage
3. allowing the samples to sit open for a period of time to equilibrate with atmospheric conditions and then sealing them until they are tested
4. mixing the samples together to minimize differences that may result from human error and from the variability of the samples

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B. This question requires the examinee to apply methods and criteria for collecting scientific data. In this case, the examinee is required to evaluate proper collection procedures for water samples that will be collected from a pond. The water samples are to be analyzed later in a laboratory for dissolved oxygen content. The dissolved oxygen content of samples can change when the water is exposed to the atmosphere, so the sample containers should be filled to the top and rapidly sealed. Since the dissolved oxygen content of pond water can vary at different locations and depths, it is important that the sampling include several locations and that these details be recorded on the containers.

They are labeled Experiment 1, Experiment 2, and Experiment 3. Each starts with a release point at the top of descending ramp A that appears to have the same slope in each, followed by a horizontal stretch that appears to be the same length in each. The horizontal stretch is followed by an ascending ramp B, with a slope that varies in each experiment. In each, the ball is shown partway up ramp B, with a label that says Stop point. The vertical position of the stop point looks the same in each experiment. In Experiment 1, ramp B is steeper than ramp A. In Experiment 2, ramp B is not at steep as ramp A. In Experiment 3, ramp B is even less steep than in Experiment 2.

A researcher conducts three experiments as shown in the diagram above. In each experiment, a ball is released at the top of Ramp A. The researcher observes the ball as it rolls down Ramp A, across a flat surface, and up Ramp B, where it eventually stops and then rolls back toward Ramp A. The researcher predicts that if Ramp B was actually flat and friction did not slow the ball, the ball would roll forever. This series of experiments most closely resembles experiments conducted by:

1. Archimedes as he developed his law of buoyant force.
2. Kepler to explain the character of planetary motions.
3. Galileo as he developed the concept of inertia.
4. Newton as he developed his third law explaining action-reaction pairs.

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C. This question requires the examinee to demonstrate knowledge of the principle of inertia developed by Galileo and the inclined plane experiments associated with that work. In his writings, Galileo noted that a ball rolling down an inclined plane and then up a second inclined plane seeks to retain its original height, regardless of the angle of the second incline. From this observation, Galileo speculated that if the second inclined plane were instead a flat, frictionless plane, the ball would continue rolling at the velocity it had attained during its descent. Galileo's idea that an object resists change to its state of motion unless acted on by a force provided the basis for Isaac Newton's law of inertia.

Which of the following technologies has been most widely used to locate offshore petroleum resources?

1. sonar
2. seismic wave reflection
3. magnetometry
4. ground-penetrating radar

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B. This question requires the examinee to analyze the interrelationship between a technology used in offshore petroleum prospecting and the laws of physics. Prospecting for petroleum resources with seismic reflection takes advantage of the differential reflection of seismic waves as they encounter different layers of material beneath the ocean floor. Sensitive instruments towed behind a boat and located below the water surface record the time it takes for the various reflected seismic waves to arrive at the recording devices. A series of these measurements can be used to identify different layers and structures beneath the ocean floor, including petroleum traps where petroleum deposits accumulate.