ACT Science Practice Test - 8 - online test

The presence of gases in earth’s atmosphere is a constant. Certain gases can absorb and hold onto heat from their environment. These gases are typically comprised of three molecules held together tenuously, which causes them to vibrate when they absorb heat. The motion of their vibrations leads to the release of their stored heat to the outside environment. The heat they release is typically quickly absorbed by other similar gases nearby. These gases remain in earth’s atmosphere for a long time after being introduced. Because of this they can trap heat within the atmosphere, preventing it from leaving, by absorbing heat and releasing heat to be absorbed by other nearby similar gases.

Hypothesis 1

Gases such as methane and nitrous oxide trap heat in the earth’s atmosphere. Trapping heat in the earth’s atmosphere leads to a greenhouse effect, gradually increasing the temperature of the earth. This increase in the earth’s temperature will lead to the melting of glaciers, increasing sea level.

Hypothesis 2

Gases such as methane but not nitrous oxide trap heat in the earth’s atmosphere. The heat methane traps in the earth’s atmosphere is less than the heat that escapes the earth leading to a global cooling effect, gradually decreasing the temperature of the earth. This decrease in earth’s temperature will lead to the development of more glaciers, decreasing sea level.

Hypothesis 3

Gases such as nitrous oxide but not methane trap heat in the earth’s atmosphere. The heat nitrous oxide traps in the earth’s atmosphere is equal to the heat that escapes the earth leaving the temperature of the earth generally unchanged. The earth’s environment will remain largely unchanged by the heat trapping properties of nitrous oxide.

Which hypothesis, if any, asserts that the effect on temperature of heat trapping gases is negligible?

Hypothesis 1

Hypothesis 2

Hypothesis 3

None of the hypotheses

(C) Hypothesis 3 is the only hypothesis that asserts the effects of heat trapping gases is negligible. Hypothesis 1 and 2 both claim that by trapping either too much heat or not enough the temperature of the earth will change. Hypothesis 3 claims that the environment of the earth will not be impacted by heat trapping gases.

Which hypothesis, if any, asserts that the effects of methane but not nitrous oxide will increase sea levels?

Hypothesis 1

Hypothesis 2

Hypothesis 3

None of the hypotheses

(D) None of the three hypotheses claim that methane but not nitrous oxide will lead to increasing sea levels. Hypothesis 1 claims the heat trapping effects of both gases will lead to increasing sea levels, but claims that this will be due to the effects of both methane and nitrous oxide. Hypothesis 2 claims methane but not nitrous oxide will affect sea levels by decreasing them, not increasing. Hypothesis 3 claims there will be no impact on sea levels.

According to the author of hypothesis 2, would it be possible for earth’s temperature to increase if the amount of heat methane traps in the atmosphere increased?

Yes, the hypothesis claims that increasing the quantity of heat will subsequently increase the quantity of heat nitrous oxide will trap

Yes, the hypothesis claims methane isn’t currently trapping a sufficient quantity of heat

No, the hypothesis claims the sea level will decrease

No, the hypothesis claims the temperature will decrease

(B) Yes, the hypothesis claims methane isn’t trapping a sufficient amount of heat. Hypothesis 2 justifies its conclusion by explaining temperature is only decreasing because methane is trapping less heat than is being released. Logically, the author of this hypothesis would support that if the inverse were true, the inverse of their conclusions would be correct.

Which statement, if true, would disprove hypothesis 3?

The sea levels of earth have been steadily rising over the past several years and will continue to do so into the foreseeable future

Methane doesn’t have a role in trapping heat, but can influence soil quality

When the heat trapping effects of both nitrous oxide and the gas carbon dioxide are considered, more heat is trapped in the earth than escapes from

The average temperature of the earth has steadily decreased over the past century, commensurate to the industrialization of the world

(C) The hypothesis would be disproved if by considering the heat trapping effects of methane and nitrous oxide, more heat is trapped in the earth than escapes. Firstly, the hypothesis claims only nitrous oxide traps heat. If methane were shown to trap heat this hypothesis would be proven false. Secondly, the hypothesis claims and bases its conclusion on the notion that the amount of heat trapped in earth generally equals the heat that escapes leading to an equilibrium. If it were observed that more heat was trapped than released, the conclusion of hypothesis 3 would be altered.

Which hypotheses operate on the assumption that gases have the potential to trap heat in earth’s atmosphere?

Hypothesis 1

Hypotheses 1 and 3

Hypotheses 2 and 3

Hypotheses 1, 2, and 3

(D) All three hypotheses operate on the assumption that gases trap heat within the earth’s atmosphere. The hypotheses disagree on the magnitude of this effect and the type of gases that trap heat. But they all agree that at least some gases have this ability.

Gasses that exist in the atmosphere remain in it for varying amounts of time. Two gases mentioned in each hypothesis, nitrous oxide and methane, have different ‘lifespans’ in the earth’s atmosphere. How do they relate?

Nitrous oxide lasts longer than methane

Methane lasts longer than nitrous oxide

Both gases last a similar time in the atmosphere

Methane technically never enters the atmosphere and therefore cannot be compared to nitrous oxide’s lifespan within the atmosphere.

(A) Nitrous oxide lasts longer than methane. It is easier and more frequent for methane to be removed from the earth’s atmosphere than nitrous oxide. In being removed, their atmospheric heat trapping potential becomes null.

In which way is hypothesis 2 similar to hypothesis 1?

Both hypotheses conclude changes in sea level can lead to problematic safety issues for cities near a sealine.

Both hypotheses conclude the earth’s temperature influences the type of heat trapping gases that can be found in the atmosphere.

Both hypotheses conclude the earth’s sea levels with change as a direct result of the heat trapping potential of nitrous oxide.

Both hypotheses conclude the temperature of the earth will change as a result of the heat trapping potential of one or more gases.

(D) Both hypotheses 1 and 2 conclude the temperature of the earth will change as a result of the heat trapping potential of one or more gases. Neither hypothesis mentioned safety issues for cities near sealines. Additionally, neither claim that temperature influences gas, they claim that gas influences temperature. Hypothesis 2 does not believe nitrous oxide has a role in heat trapping, making answer C incorrect.

Researchers studied sprinting ability to better understand differences between individuals in performance. After completion of the first study, researchers performed two follow up studies to explore the movement economy of and physiological response to sprinting. The same five subjects were used for each study.

Study 1

Five healthy adult subjects with similar body weight and height were familiarized with the sprinting technique. Each subject was instructed to sprint as fast as they could in a linear path for 20 yards. Infrared timing gates were placed at 5 yards (G1), 10 yards (G2), 15 yards (G3), and 20 yards (G4) into the route to record timing and later extrapolate speed.

Science lesson Science Practice Test 8 exam questions 8. question pragraph

Study 2

The five healthy adult subjects from Study 1 were instructed to sprint as fast as they could in a linear path for 15 yards. An in-ground force plate was inserted on the route at the 10-yard point with the capacity to measure peak propulsive and braking forces in newtons. Propulsive forces have vectors in the +y direction and contribute to acceleration while sprinting. Braking forces have vectors in the -y direction and contribute to deceleration while sprinting.

Science lesson Science Practice Test 8 exam questions 8. question pragraph

Study 3

The five healthy adult subjects from Study 1 and Study 2 were instructed to sprint as fast as they could in a linear path until they could no longer do so. Immediately after completion of their route blood samples were extracted from subjects. Blood samples were analyzed to measure concentration of blood lactate: larger quantities are a known biomarker for muscular fatigue.

Science lesson Science Practice Test 8 exam questions 8. question pragraph

What is the most likely reason the same five subjects were used for each study?

It was more convenient given the subjects were already familiarized with the sprinting technique from Study 1

It prevents an out-group homogeneity effect

It allows for within-subjects comparisons across studies

It decreases external validity of the studies, making them more reliable

(C) Using the same five subjects for each study allows for within-subjects comparisons across studies. If different subjects were used variability between individuals could confound cross analysis of studies. As an example, it can be observed the slowest 20-yard sprinter had the lowest net peak propulsive force (peak propulsive force - peak braking force) although they had the highest peak propulsive force. If that subject did not return this observation could not be made.

In Study 2, which subject is suggested to be moving fastest based on peak propulsive and braking forces?

Subject 1

Subject 3

Subject 4

Subject 5

(B) Subject 3 was suggested to be moving fastest according to Study 2. They exhibited the greatest net peak propulsive force (76 Newtons), which means they are producing more force to propel them in the +y direction than their counterparts in the study. Because body weight is similar between subjects it can be assumed this means they are traveling faster.

Suppose the peak propulsive force of Subject 3 had been lesser than their peak braking force between G3 and G4, what would this signify?

The subject would be traveling backwards.

The subject would be traveling at a constant velocity.

The subject would be accelerating.

The subject would be decelerating.

(D) Subject 3 would have been decelerating. Regardless of the point in the sprint it occurred, having a greater peak braking force than peak propulsive force means that in that moment deceleration is occurring. Because the subject was still sprinting between G3 and G4 it can be assumed they were traveling in the +y direction at the time this occurred. If they were standing still they would be accelerating in the -y direction. Because they were in motion net force in the -y direction must first decelerate them until they reach a velocity of 0 yds/s before they are considered to be accelerating in the -y direction.

Based on the three studies, what can be observed about the role of local muscular fatigue on 20-yard sprint performance?

The fastest sprinters demonstrate more local muscular fatigue after sprinting according to blood lactate concentration.

The fastest sprinters demonstrate less local muscular fatigue after sprinting according to blood lactate concentration.

The fastest sprinters demonstrate more local muscular fatigue after sprinting according to peak propulsive forces produced.

The fastest sprinters demonstrated less local muscular fatigue after sprinting according to peak braking forces produced.

(B) The fastest sprinters demonstrate less local muscular fatigue after sprinting according to blood lactate concentration. Because the question refers to 20-yard sprint performance only consider the sprinters times at G4. Those with the fastest times have the lowest blood lactate concentrations, and those with the slowest times have the highest.

Which of the following is a major flaw in the design of Study 2?

Subjects ran 15 yards instead of 5 yards.

The infrared timing gates were placed at positions different than in Study 1.

Force data was only collected at a single point and was not representative of sprinting ability over the entirety of a 20-yard distance.

Blood samples were taken immediately after sprinting because subjects were still sweating and could contaminate the sample.

(C) Force data was only collected at a single point and was not representative of sprinting ability over the entirety of a 20-yard distance. If force data were collected for every step taken by subjects, then a more complete picture of their movement economy can be painted. Currently, data only represents a 5-millisecond period of the sprint. If a subject produced more braking force at the 15-yard point than 10 yard, or more propulsive force at the 5-yard point than 10 yards, it cannot be observed. Answers B and D do not relate to Study 2, and answer A would not have helped the study.

In Study 1, which subject traveled fastest between G3 and G4?

Subject 1

Subject 2

Subject 3

Subject 5

(A) In Study 1, Subject 1 ran fastest between G3 and G4. Do not consider overall sprint times, instead subtract G3 times from G4 times. This will provide the amount of time each subject took to run those five yards.