How to find research summary in physics - ACT Science

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Question

A physicist performs a series of experiments to determine the relative magnitude of electric charge on four particles. A given particle is considered to have a higher magnitude of charge than another if it will push out (or draw in) a positive test charge farther than the other particle.

A particle that pushes the test charge has positive charge, while a particle that pulls (or draws in) the test charge has negative charge. This is known as the sign of the charge. Magnitude of charge is unrelated to sign.

The experiment is conducted on a horizontal axis that measures from 20m in total: from –10m on the left to +10m on the right, with a measurement of 0m in the middle.

Experiment 1

Particle A is placed at position –5m on the horizontal axis. The test charge has a specific magnitude of charge and is located at +3m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

Experiment 2

Particle B is placed at position –8m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at 0m on that same axis. The result of the experiment is that the test charge is displaced to –7.5m.

Experiment 3

Particle C is placed at position 0m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +8m on that same axis. The result of the experiment is that the test charge is displaced to +10m.

Experiment 4

Particle D is placed at position –5.5m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +2.5m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

It can be inferred from the experiment that __________.

Answer

Subtract the position of the particle from the initial position of the test charge.

In each experiment the result is 8m.

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Question

A physicist performs a series of experiments to determine the relative magnitude of electric charge on four particles. A given particle is considered to have a higher magnitude of charge than another if it will push out (or draw in) a positive test charge farther than the other particle.

A particle that pushes the test charge has positive charge, while a particle that pulls (or draws in) the test charge has negative charge. This is known as the sign of the charge. Magnitude of charge is unrelated to sign.

The experiment is conducted on a horizontal axis that measures from 20m in total: from –10m on the left to +10m on the right, with a measurement of 0m in the middle.

Experiment 1

Particle A is placed at position –5m on the horizontal axis. The test charge has a specific magnitude of charge and is located at +3m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

Experiment 2

Particle B is placed at position –8m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at 0m on that same axis. The result of the experiment is that the test charge is displaced to –7.5m.

Experiment 3

Particle C is placed at position 0m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +8m on that same axis. The result of the experiment is that the test charge is displaced to +10m.

Experiment 4

Particle D is placed at position –5.5m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +2.5m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

The results of Experiment 1 and 2 show that __________.

Answer

Particle A has a lower magnitude of charge than particle B because it displaced the test charge by a smaller amount.

In experiment 1, the test charge moved from +3m to +7.5m, a difference of 4.5m.

In experiment 2, the test charge moved from 0m to –7.5m, a difference of 7.5m.

The experiments give no insight into charge density.

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Question

A physicist performs a series of experiments to determine the relative magnitude of electric charge on four particles. A given particle is considered to have a higher magnitude of charge than another if it will push out (or draw in) a positive test charge farther than the other particle.

A particle that pushes the test charge has positive charge, while a particle that pulls (or draws in) the test charge has negative charge. This is known as the sign of the charge. Magnitude of charge is unrelated to sign.

The experiment is conducted on a horizontal axis that measures from 20m in total: from –10m on the left to +10m on the right, with a measurement of 0m in the middle.

Experiment 1

Particle A is placed at position –5m on the horizontal axis. The test charge has a specific magnitude of charge and is located at +3m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

Experiment 2

Particle B is placed at position –8m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at 0m on that same axis. The result of the experiment is that the test charge is displaced to –7.5m.

Experiment 3

Particle C is placed at position 0m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +8m on that same axis. The result of the experiment is that the test charge is displaced to +10m.

Experiment 4

Particle D is placed at position –5.5m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +2.5m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

Which of the particles is negatively charged?

Answer

All of the particles are initially placed to the left of the test charge. Particle B is the only one that "draws in" the test charge to the left, from 0m to –7.5m (we are told initially that the axis runs from –10m on the left to 10m on the right, with 0m in the middle).

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Question

A physicist performs a series of experiments to determine the relative magnitude of electric charge on four particles. A given particle is considered to have a higher magnitude of charge than another if it will push out (or draw in) a positive test charge farther than the other particle.

A particle that pushes the test charge has positive charge, while a particle that pulls (or draws in) the test charge has negative charge. This is known as the sign of the charge. Magnitude of charge is unrelated to sign.

The experiment is conducted on a horizontal axis that measures from 20m in total: from –10m on the left to +10m on the right, with a measurement of 0m in the middle.

Experiment 1

Particle A is placed at position –5m on the horizontal axis. The test charge has a specific magnitude of charge and is located at +3m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

Experiment 2

Particle B is placed at position –8m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at 0m on that same axis. The result of the experiment is that the test charge is displaced to –7.5m.

Experiment 3

Particle C is placed at position 0m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +8m on that same axis. The result of the experiment is that the test charge is displaced to +10m.

Experiment 4

Particle D is placed at position –5.5m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +2.5m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

If particle C and particle D are placed on the axis at the same time, accoring to the results of the experiment, what is likely to occur?

Answer

The best answer is that they would push (repel) each other. We know from the effects of a positive particle on a positive test charge that like signs repel and unlike signs draw in (attract) each other.

We know the two particles have the same sign (possitive) because of how they affect the test charge in the experiments.

We cannot speculate about how the combined effect of their relative charges would displace a test charge without knowing their exact locations on the axis.

We know that there must be some reaction.

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Question

A physicist performs a series of experiments to determine the relative magnitude of electric charge on four particles. A given particle is considered to have a higher magnitude of charge than another if it will push out (or draw in) a positive test charge farther than the other particle.

A particle that pushes the test charge has positive charge, while a particle that pulls (or draws in) the test charge has negative charge. This is known as the sign of the charge. Magnitude of charge is unrelated to sign.

The experiment is conducted on a horizontal axis that measures from 20m in total: from –10m on the left to +10m on the right, with a measurement of 0m in the middle.

Experiment 1

Particle A is placed at position –5m on the horizontal axis. The test charge has a specific magnitude of charge and is located at +3m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

Experiment 2

Particle B is placed at position –8m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at 0m on that same axis. The result of the experiment is that the test charge is displaced to –7.5m.

Experiment 3

Particle C is placed at position 0m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +8m on that same axis. The result of the experiment is that the test charge is displaced to +10m.

Experiment 4

Particle D is placed at position –5.5m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +2.5m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

The results of experiments 3 and 4 show that __________.

Answer

We know that particles D and C have the same sign, as they pushed the test charge in the same direction.

We know that D has the higher magnitude because it displaced the test charge from +2.5m to +7.5m, a difference of 5m, while C displaced the test charge from +8m to +10m, a difference of 2m.

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Question

A physicist performs a series of experiments to determine the relative magnitude of electric charge on four particles. A given particle is considered to have a higher magnitude of charge than another if it will push out (or draw in) a positive test charge farther than the other particle.

A particle that pushes the test charge has positive charge, while a particle that pulls (or draws in) the test charge has negative charge. This is known as the sign of the charge. Magnitude of charge is unrelated to sign.

The experiment is conducted on a horizontal axis that measures from 20m in total: from –10m on the left to +10m on the right, with a measurement of 0m in the middle.

Experiment 1

Particle A is placed at position –5m on the horizontal axis. The test charge has a specific magnitude of charge and is located at +3m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

Experiment 2

Particle B is placed at position –8m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at 0m on that same axis. The result of the experiment is that the test charge is displaced to –7.5m.

Experiment 3

Particle C is placed at position 0m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +8m on that same axis. The result of the experiment is that the test charge is displaced to +10m.

Experiment 4

Particle D is placed at position –5.5m on the horizontal axis. The test charge has the same magnitude of charge as the previous experiment and is located at +2.5m on that same axis. The result of the experiment is that the test charge is displaced to +7.5m.

Which of the following represents the order of charge of the four particles, from highest to lowest?

Answer

Particle B displaced the test charge from 0m to –7.5m, a distance of 7.5m

Particle D displaced the test charge from +2.5m to +7.5m, a distance of 5m

Particle A displaced the test charge from +3m to +7.5m, a distance of 4.5m

Particle C displaced the test charge from +8m to +10m, a distance of 2m

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Question

The photoelectric effect is a phenomenon that has led to many important scientific discoveries. Light of a particular wavelength is shined onto a piece of metal, showering the metal with photons. Wavelength is inversely related to a photon's energy. That is, with a smaller wavelength, the photon has greater energy. The wavelength of the light is decreased until a detector next to the metal senses that electrons are being ejected from the metal. This sensor also tells us how many electrons are ejected per second, which we call electrical current. At this point, any additional decrease in wavelength does not affect the number of electrons ejected. This point is called the metal's work function. However, if we then begin to increase the intensity of the light being shone (meaning the amount of light as opposed to the light's wavelength), the number of electrons picked up by the sensor increases.

Based on the information in the passage, the term "work function" can be most accurately described as which of the following?

Answer

The correct answer is that it is the point at which the energy of the photons is barely enough to eject electrons. We know this because, as the passage says, decreasing the wavelength (increasing the energy) of the photons does not eject electrons until exactly this point. This implies that this gradual increase in photon energy passed the threshold we are calling the "work function" and led to electrons being ejected.

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Question

The photoelectric effect is a phenomenon that has led to many important scientific discoveries. Light of a particular wavelength is shined onto a piece of metal, showering the metal with photons. Wavelength is inversely related to a photon's energy. That is, with a smaller wavelength, the photon has greater energy. The wavelength of the light is decreased until a detector next to the metal senses that electrons are being ejected from the metal. This sensor also tells us how many electrons are ejected per second, which we call electrical current. At this point, any additional decrease in wavelength does not affect the number of electrons ejected. This point is called the metal's work function. However, if we then begin to increase the intensity of the light being shone (meaning the amount of light as opposed to the light's wavelength), the number of electrons picked up by the sensor increases.

According to the information in the passage, what can we infer would happen if the intensity of the light were decreased immediately after reaching the work function?

Answer

The correct answer is that the current would remain, but it would decrease. At the end of the passage, we are told that intensity of the light affects the current in a direct relationship. That is, more intensity means greater current. Therefore, as we have seen that the presence of a current is related to the wavelength of the light used, we know that the current would remain. Furthermore, as we have decreased the intensity, we know that this current would simply decrease.

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Question

The photoelectric effect is a phenomenon that has led to many important scientific discoveries. Light of a particular wavelength is shined onto a piece of metal, showering the metal with photons. Wavelength is inversely related to a photon's energy. That is, with a smaller wavelength, the photon has greater energy. The wavelength of the light is decreased until a detector next to the metal senses that electrons are being ejected from the metal. This sensor also tells us how many electrons are ejected per second, which we call electrical current. At this point, any additional decrease in wavelength does not affect the number of electrons ejected. This point is called the metal's work function. However, if we then begin to increase the intensity of the light being shone (meaning the amount of light as opposed to the light's wavelength), the number of electrons picked up by the sensor increases.

Light intensity can best be described as which of the following?

Answer

The correct answer is the number of photons. In the passage, we are told that the intensity of a light is related to the amount of light used. As light can be quantified in terms of photons, we know that this means that more intensity implies more photons. Any answer related to energy (including wavelength, force, and color) are incorrect because energy does not directly affect number of photons emitted and the speed of light is always the same.

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Question

A particle accelerator functions by exerting a magnetic field on charged particles which are shot into the accelerator. The magnetic field causes the charged particles to move around in a circle of radius that can be predicted by the following equation, where is the mass of the particle in kilograms, is the initial speed at which the particle was shot in meters per second, is the charge of the particle in Coulombs, and is the strength of the magnetic field in Tesla.

If a given magnetic field's strength and its radius , what would the radius be at ?

Answer

The correct answer is . We know by the equation that and are inversely related. As one increases, the other decreases, and vice versa. Therefore, if is tripled, must be divided by .

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Question

A particle accelerator functions by exerting a magnetic field on charged particles which are shot into the accelerator. The magnetic field causes the charged particles to move around in a circle of radius that can be predicted by the following equation, where is the mass of the particle in kilograms, is the initial speed at which the particle was shot in meters per second, is the charge of the particle in Coulombs, and is the strength of the magnetic field in Tesla.

A proton weighs approximately amu (atomic mass units) and has a charge of C. An electron has the same magnitude of charge, but it has about of the proton's mass. What would happen to radius if we were to suddenly switch the particle in the accelerator from a proton to an electron, keeping all of the other conditions the same?

Answer

The correct answer is that radius would decrease -fold. With a smaller mass, we know by the given equation that the radius would change in proportion with the change in particle mass. Therefore, if the mass decreased -fold, so would radius .

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Question

A particle separator functions by using a magnetic field and an electric field pointing perpendicularly. When a charged particle is launched into the particle separator, a constant electric force is exerted on the particle proportional to the particle's charge. Additionally, the magnetic field exerts a force on the particle that is in the opposite direction of the electric force and that is proportional to the particle's charge and velocity. A particle will make it through the particle separator only if the opposing magnetic forces and electric forces are equal in magnitude as they will not cause a net change in the particle's direction.

What can we infer would happen if a proton (a particle with a positive charge) were shot into the particle accelerator with an extremely low speed?

Answer

The correct answer is that the particle would move in the direction of the electric force. For this question, it is important to remember that we are inferring. This is a key skill in scientific research. Although we do not know the exact parameters, since we know that the magnetic force depends on bothvelocity and charge, we can make the inference that with a low velocity, the proton will not experience a strong magnetic force. Therefore, it is most probable that the particle will move in the same direction as the force produced by the electric field.

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Question

Sound waves travel through a medium by mechanically disturbing the particles of that medium. As particles in the medium are displaced by the sound wave, they in turn act upon neighboring particles. In this fashion, the wave travels through the medium through a parallel series of disturbed particles. Like in other forms of motion, the rate at which the sound wave travels can be measured by dividing the distance over which the wave travels by the time required for it to do so.

Study 1
A group of students hypothesizes that the velocity of sound is dependent upon the density of the medium through which it passes. They propose that with more matter in a given space, each particle needs to travel a shorter distance to disturb the adjacent particles. Using two microphones and a high speed recording device, the students measured the delay from the first microphone to the second. They chose a variety of media, shown in Table 1, and measured the velocity of sound through each using their two-microphone setup. The results are found in Table 1.

Sound_table_1

Study 2
The students wanted to test their hypothesis by using the same medium at different densities. To do this, they heated pure water to various temperatures and repeated the procedure described in Study 1. Their results can be found in Table 2.

Sound_table_2

If the temperature of iron were raised slightly in Study 1, what would be the most likely result?

Answer

Based on the results of Study 2, one can infer that increases in temperature tend to cause density to decrease and velocity to increase. Because this is the only temperature information in the passage, it is the best predictor of the effect of temperature change in iron.

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Question

Sound waves travel through a medium by mechanically disturbing the particles of that medium. As particles in the medium are displaced by the sound wave, they in turn act upon neighboring particles. In this fashion, the wave travels through the medium through a parallel series of disturbed particles. Like in other forms of motion, the rate at which the sound wave travels can be measured by dividing the distance over which the wave travels by the time required for it to do so.

Study 1
A group of students hypothesizes that the velocity of sound is dependent upon the density of the medium through which it passes. They propose that with more matter in a given space, each particle needs to travel a shorter distance to disturb the adjacent particles. Using two microphones and a high speed recording device, the students measured the delay from the first microphone to the second. They chose a variety of media, shown in Table 1, and measured the velocity of sound through each using their two-microphone setup. The results are found in Table 1.

Sound_table_1

Study 2
The students wanted to test their hypothesis by using the same medium at different densities. To do this, they heated pure water to various temperatures and repeated the procedure described in Study 1. Their results can be found in Table 2.

Sound_table_2

Which study provides stronger evidence against the students' prediction and why?

Answer

The students in the passage hypothesized that increased density would result in increased velocity of sound through that medium. Study 2 provides the most evidence to the contrary by showing decreasing densities linked to increasing velocities.

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Question

Sound waves travel through a medium by mechanically disturbing the particles of that medium. As particles in the medium are displaced by the sound wave, they in turn act upon neighboring particles. In this fashion, the wave travels through the medium through a parallel series of disturbed particles. Like in other forms of motion, the rate at which the sound wave travels can be measured by dividing the distance over which the wave travels by the time required for it to do so.

Study 1
A group of students hypothesizes that the velocity of sound is dependent upon the density of the medium through which it passes. They propose that with more matter in a given space, each particle needs to travel a shorter distance to disturb the adjacent particles. Using two microphones and a high speed recording device, the students measured the delay from the first microphone to the second. They chose a variety of media, shown in Table 1, and measured the velocity of sound through each using their two-microphone setup. The results are found in Table 1.

Sound_table_1

Study 2
The students wanted to test their hypothesis by using the same medium at different densities. To do this, they heated pure water to various temperatures and repeated the procedure described in Study 1. Their results can be found in Table 2.

Sound_table_2

According to the information in the passage, what is necessary for sound to travel through a medium?

Answer

The passage states that sound waves travel by mechanically disturbing particles. Without a medium with particles close enough to interact physically, there would be no transfer of mechanical energy through the medium.

The remaining answers list conditions of the studies used to test the students' hypothesis about density and sound velocity. These are not essential for sound to travel through a medium.

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Question

Sound waves travel through a medium by mechanically disturbing the particles of that medium. As particles in the medium are displaced by the sound wave, they in turn act upon neighboring particles. In this fashion, the wave travels through the medium through a parallel series of disturbed particles. Like in other forms of motion, the rate at which the sound wave travels can be measured by dividing the distance over which the wave travels by the time required for it to do so.

Study 1
A group of students hypothesizes that the velocity of sound is dependent upon the density of the medium through which it passes. They propose that with more matter in a given space, each particle needs to travel a shorter distance to disturb the adjacent particles. Using two microphones and a high speed recording device, the students measured the delay from the first microphone to the second. They chose a variety of media, shown in Table 1, and measured the velocity of sound through each using their two-microphone setup. The results are found in Table 1.

Sound_table_1

Study 2
The students wanted to test their hypothesis by using the same medium at different densities. To do this, they heated pure water to various temperatures and repeated the procedure described in Study 1. Their results can be found in Table 2.

Sound_table_2

In Study 1, if the students were to double the length of the samples of media, what would happen to the velocity of sound through those media?

Answer

According to the passage, velocity of sound is found by dividing distance by time. Any increase in distance traveled would cause the time required for travel to increase proportionally. In this manner, velocity would remain constant if the students were to double the length of media samples in Study 1.

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Question

A physicist wishes to study the trajectory of a ball launched horizontally. She varies parameters such as the launching velocity, starting height, and mass of the ball. For each trajectory, she records the time of flight (in seconds) and horizontal displacement (in meters). She assumes air resistance is negligible.

Figure 1

Screen_shot_2015-03-13_at_3.42.31_pm

Using all of the data she collects, she constructs the following table:

Table 1

Screen_shot_2015-03-13_at_3.43.04_pm

Based on the data presented in the table, what appears to be the relationship between the mass of the ball and the time of flight?

Answer

In trial 3, the time of flight remains the same as the mass of the ball is varied.

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Question

A physicist wishes to study the trajectory of a ball launched horizontally. She varies parameters such as the launching velocity, starting height, and mass of the ball. For each trajectory, she records the time of flight (in seconds) and horizontal displacement (in meters). She assumes air resistance is negligible.

Figure 1

Screen_shot_2015-03-13_at_3.42.31_pm

Using all of the data she collects, she constructs the following table:

Table 1

Screen_shot_2015-03-13_at_3.43.04_pm

In which trial(s) did the time of flight change between data points?

Answer

By inspecting the table, we see that the time of flight changed between data points for Trial 2 only.

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Question

Pendulum

The period of a simple pendulum is defined as the amount of time that it takes for a pendulum to swing from one end to the other and back. In studying the period of a simple pendulum, two students express their opinions.

Student 1: The period of a pendulum depends on two factors: the mass of the pendulum's bob (the object swinging at the end of the pendulum) and the length of the pendulum. The height at which the pendulum is originally dropped does not affect the period .

Student 2: The period of a pendulum only depends on the length of the pendulum. Varying the mass and the height at which the pendulum is originally dropped does not affect how long the pendulum takes to swing across.

The two students ran a series of trials to measure the period of a simple pendulum using varying weights and lengths. The students did not measure height as a factor. The results of the trials can be seen in the table below:

Table2

According to the data presented, what is the apparent relationship between mass and period ?

Answer

The correct answer is that they are not related. For this question, the most important row in the presented table is the last row, because it demonstrates that changing the mass of the bob had no effect on the period of the pendulum. Increasing the mass of the bob by 4 kilograms did not affect the pendulum's period. Note that this is done while keeping the length of the pendulum constant. Therefore, we conclude that there is no correlation between the mass of a pendulum's bob, , and the pendulum's period, . This is indeed true experimentally.

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Question

Pendulum

The period of a simple pendulum is defined as the amount of time that it takes for a pendulum to swing from one end to the other and back. In studying the period of a simple pendulum, two students express their opinions.

Student 1: The period of a pendulum depends on two factors: the mass of the pendulum's bob (the object swinging at the end of the pendulum) and the length of the pendulum. The height at which the pendulum is originally dropped does not affect the period .

Student 2: The period of a pendulum only depends on the length of the pendulum. Varying the mass and the height at which the pendulum is originally dropped does not affect how long the pendulum takes to swing across.

The two students ran a series of trials to measure the period of a simple pendulum using varying weights and lengths. The students did not measure height as a factor. The results of the trials can be seen in the table below:

Table2

According to the data, what is the apparent relationship between length and period ?

Answer

The correct answer is that they are positively and non-linearly related. We can ignore the change in mass because the last two rows of the chart demonstrate that changing the mass of a pendulum's bob does not affect the period of the pendulum. As we can see in the chart, once we ignore the changing mass, we see that increasing the length by a factor of four only tends to increase the period by a factor of two. This shows a non-linear but still positive correlation. Although it wouldn't be hard to discern what exactly this non-linear relationship is, all we need for this question is to know that it is non-linear.

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