How to find research summary in physics
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ACT Science › How to find research summary in physics
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 
If a given magnetic field's strength 
Explanation
The correct answer is 
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 __________.
All particles are placed an equal distance from the test charge.
Particle A and particle D have equal sign and magnitude.
Particle A and particle B have equal sign and magnitude.
All particles have an equal charge density.
Explanation
Subtract the position of the particle from the initial position of the test charge.
In each experiment the result is 8m.
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.
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.
Which study provides stronger evidence against the students' prediction and why?
Study 2, because using the same medium shows that velocity increases as density decreases
Study 2, because using the same medium shows that velocity decreases as density decreases
Study 1, because using different media shows that velocity increases as density decreases
Study 1, because using different media shows that velocity increases as density increases
Explanation
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.
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
Using all of the data she collects, she constructs the following table:
Table 1
In which trial(s) did the time of flight change between data points?
Trial 2 only
Trials 2 and 3
Trial 3 only
Trials 1 and 2
Explanation
By inspecting the table, we see that the time of flight changed between data points for Trial 2 only.
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 __________.
Particle A has a lower magnitude of charge than particle B.
Particle A has a higher magnitude of charge than particle B.
Particle A has the same magnitude of charge as particle B.
Particle A has a lower charge density than particle B.
Explanation
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.
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?
Particle B
Particle A
Particle C
Particle D
Explanation
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).
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?
The particle would be pushed in the direction of the electric force.
The particle would slow to a stop.
The particle would eventually make it out of the particle separator.
The particle would be pushed in the direction of the magnetic force.
The particle would accelerate.
Explanation
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.
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.
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.
If the temperature of iron were raised slightly in Study 1, what would be the most likely result?
Velocity would increase.
Velocity would decrease.
Density would increase.
Velocity would remain constant.
Explanation
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.
The period of a simple pendulum 
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 
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:
According to the data presented, what is the apparent relationship between mass 
The two variables are not related.
The two variables have a positive linear correlation
The two variables have negative linear correlation
The two variables have a positive non-linear correlation
The two variables have a negative non-linear correlation
Explanation
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, 
Engineers are evaluating four potential technologies. These technologies are to be used as power plants that are considered "clean" energy. The estimated energy output of these plants were calculated and the resources needed to run these were also listed.
In a desert region, which two technologies can possibly be used?
A and B
A and C
B and D
A and D
Explanation
In a desert area there is no access to water. Therefore any technologies involving the use of water cannot be used efficiently if at all. This leaves the technologies that only require the sun or wind. The correct answer is therefore A and B.