ACT Science : Physics

Study concepts, example questions & explanations for ACT Science

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Example Questions

Example Question #1245 : Act Science

A scientist is exploring the nature of energy and work in two experimental systems.

Experiment 1

She first sets up a system with a ball on an inclined plane, and calculates the potential and kinetic energies of the ball at three positions. She places the ball at position 1, stops the ball after rolling to position 2, and then again allows it to roll to position 3. The measured kinetic and potential energies are shown in the table, along with measurements of the force of friction acting on the ball.

 

Ball Position

Potential Energy

Kinetic Energy

Force of Friction

       1

       150 kJ

       X kJ

         0 N

       2

        75 kJ

      75 kJ

         0 N

       3

         X kJ

      150 kJ

         0 N

 

Experiment 2

The same scientist then sets up another experiment with the same ball, again at three positions. The ball is provided a slight push, and then allowed to roll down three levels without any additional external input of energy.

She uses the following formulae to calculate the energy levels of the ball:

Potential Energy = Mass of the Ball x Acceleration Due to Gravity x Height of the Ball

Kinetic Energy = (1/2) x Mass of the Ball x (Velocity of the Ball)2

She also measures the internal energy of the ball, a value that she defines as the amount of energy contained in the motion of the molecules that make up the matter of the ball.

Untitled2

Position

Potential Energy

  Velocity

Internal Energy

1

A

1 m/s

5 kJ

2

B

5.47 m/s

6 kJ

3

C

10.94 m/s

 7 kJ

In Experiment 1, if the vertical distance drop is the same from points 2 to 3 as it is from points 1 to 2, which of the following most nearly approximates the value of X?

Possible Answers:

38 kJ

0 kJ

50 kJ

25 kJ

Correct answer:

38 kJ

Explanation:

The magnitude of the height drop is the same as the previous drop, which halved the potential energy. According to the formula in Experiment 2, we should again halve the potential energy, yielding a new potential energy value of 37.5 kJ, or approximately 38 kJ.

Example Question #61 : How To Find Synthesis Of Data In Physics

A scientist is exploring the nature of energy and work in two experimental systems.

Experiment 1

She first sets up a system with a ball on an inclined plane, and calculates the potential and kinetic energies of the ball at three positions. She places the ball at position 1, stops the ball after rolling to position 2, and then again allows it to roll to position 3. The measured kinetic and potential energies are shown in the table, along with measurements of the force of friction acting on the ball.

 

Ball Position

Potential Energy

Kinetic Energy

Force of Friction

1

150 kJ

X kJ

0 N

2

75 kJ

75 kJ

0 N

3

X kJ

150 kJ

0 N

 

Experiment 2

The same scientist then sets up another experiment with the same ball, again at three positions. The ball is provided a slight push, and then allowed to roll down three levels without any additional external input of energy.

She uses the following formulae to calculate the energy levels of the ball:

Potential Energy = Mass of the Ball x Acceleration Due to Gravity x Height of the Ball

Kinetic Energy = (1/2) x Mass of the Ball x (Velocity of the Ball)2

She also measures the internal energy of the ball, a value that she defines as the amount of energy contained in the motion of the molecules that make up the matter of the ball.

Untitled2

Position

Potential Energy

  Velocity

Internal Energy

1

A

1 m/s

5 kJ

2

B

5.47 m/s

6 kJ

3

C

10.94 m/s

7 kJ

The Law of Conservation of Energy states that energy in the universe cannot be created or destroyed. Which of the following is most likely true in Experiment 2 as the ball moves from position 1 to position 3?

Possible Answers:

All the kinetic energy lost from position 1 appears as potential energy at position 3.

Except for 2 kJ, all of the potential energy lost from position 1 appears as kinetic energy at position 3.

All the kinetic energy lost from position 1 appears as kinetic energy at position 3.

All the potential energy lost from position 1 appears as kinetic energy at position 3.

Correct answer:

Except for 2 kJ, all of the potential energy lost from position 1 appears as kinetic energy at position 3.

Explanation:

The Law of Conervation of Energy states that we cannot create or destroy energy, only that it can change form. Thus, the kinetic energy that appears as increased velocity of the ball at position 3 must come from the potential energy of the ball at position 1. However, since the ball saw an increase in internal energy as well, this 2 kJ increase must be deducted from the final increase in kinetic energy at position 3. 

Example Question #63 : How To Find Synthesis Of Data In Physics

A scientist is exploring the nature of energy and work in two experimental systems.

Experiment 1

She first sets up a system with a ball on an inclined plane, and calculates the potential and kinetic energies of the ball at three positions. She places the ball at position 1, stops the ball after rolling to position 2, and then again allows it to roll to position 3. The measured kinetic and potential energies are shown in the table, along with measurements of the force of friction acting on the ball.

 

Ball Position

Potential Energy

Kinetic Energy

Force of Friction

1

150 kJ

X kJ

0 N

2

75 kJ

75 kJ

0 N

3

X kJ

150 kJ

0 N

 

Experiment 2

The same scientist then sets up another experiment with the same ball, again at three positions. The ball is provided a slight push, and then allowed to roll down three levels without any additional external input of energy.

She uses the following formulae to calculate the energy levels of the ball:

Potential Energy = Mass of the Ball x Acceleration Due to Gravity x Height of the Ball

Kinetic Energy = (1/2) x Mass of the Ball x (Velocity of the Ball)2

She also measures the internal energy of the ball, a value that she defines as the amount of energy contained in the motion of the molecules that make up the matter of the ball.

Untitled2

Position

Potential Energy

  Velocity

Internal Energy

1

A

1 m/s

5 kJ

2

B

5.47 m/s

6 kJ

3

C

10.94 m/s

7 kJ

The work-energy theorem states that the work done on an object is equal to that object's change in kinetic energy:  

As the ball rolls from position 1 to position 2 in Experiment 1, which of the following is most likely true?

Possible Answers:

The work done on the ball is negative.

The work done on the ball is 0.

The work done on the ball is positive.

The work done on the ball is 1.

Correct answer:

The work done on the ball is positive.

Explanation:

The passage states that the ball has a change in kinetic energy that is positive as it rolls down the ramp. Based on the equation in the question, this means that the work done on the ball must also be positive.

Example Question #64 : How To Find Synthesis Of Data In Physics

A scientist is exploring the nature of energy and work in two experimental systems.

Experiment 1

She first sets up a system with a ball on an inclined plane, and calculates the potential and kinetic energies of the ball at three positions. She places the ball at position 1, stops the ball after rolling to position 2, and then again allows it to roll to position 3. The measured kinetic and potential energies are shown in the table, along with measurements of the force of friction acting on the ball.

 

Ball Position

Potential Energy

Kinetic Energy

Force of Friction

       1

      150 kJ

       X kJ

        0 N

       2

       75 kJ

      75 kJ

        0 N

       3

        X kJ

     150 kJ

        0 N

 

Experiment 2

The same scientist then sets up another experiment with the same ball, again at three positions. The ball is provided a slight push, and then allowed to roll down three levels without any additional external input of energy.

She uses the following formulae to calculate the energy levels of the ball:

Potential Energy = Mass of the Ball x Acceleration Due to Gravity x Height of the Ball

Kinetic Energy = (1/2) x Mass of the Ball x (Velocity of the Ball)2

She also measures the internal energy of the ball, a value that she defines as the amount of energy contained in the motion of the molecules that make up the matter of the ball.

Untitled2

Position

Potential Energy

  Velocity

Internal Energy

1

A

1 m/s

5 kJ

2

B

5.47 m/s

6 kJ

3

C

10.94 m/s

7 kJ

As the velocity of an object is increased fourfold, its kinetic energy most likely increases by a factor of:

Possible Answers:

8

16

4

2

Correct answer:

16

Explanation:

The formula in the passage states that the increase in velocity is squared to find in the change in kinetic energy. Thus, if you quadruple the velocity, you increase the overal kinetic energy by a factor of 16.

Example Question #1254 : Act Science

A scientist is exploring the nature of energy and work in two experimental systems.

Experiment 1

She first sets up a system with a ball on an inclined plane, and calculates the potential and kinetic energies of the ball at three positions. She places the ball at position 1, stops the ball after rolling to position 2, and then again allows it to roll to position 3. The measured kinetic and potential energies are shown in the associated table, along with measurements of the force of friction acting on the ball.

 

Ball Position

Potential Energy

Kinetic Energy

Force of Friction

       1

      150 kJ

       X kJ

         0 N

       2

       75 kJ

      75 kJ

         0 N

       3

        X kJ

     150 kJ

         0 N

 

Experiment 2

The same scientist then sets up another experiment with the same ball, again at three positions. The ball is provided a slight push, and then allowed to roll down three levels without any additional external input of energy.

She uses the following formulae to calculate the energy levels of the ball:

Potential Energy = Mass of the Ball x Acceleration Due to Gravity x Height of the Ball

Kinetic Energy = (1/2) x Mass of the Ball x (Velocity of the Ball)2

She also measures the internal energy of the ball, a value that she defines as the amount of energy contained in the motion of the molecules that make up the matter of the ball.

Untitled2

Position

Potential Energy

  Velocity

Internal Energy

1

A

1 m/s

5 kJ

2

B

5.47 m/s

6 kJ

3

C

10.94 m/s

7 kJ

As the height of an object is increased fourfold, its potential energy most likely increases by a factor of:

Possible Answers:

2

16

32

4

Correct answer:

4

Explanation:

Unlike kinetic energy, the formula for potential energy in the passage indicates that the potential energy is only directly proportional to the height of the object, not its square. Thus, the potential energy increases by the same factor as the height increases.

Example Question #61 : How To Find Synthesis Of Data In Physics

Experiment 1

A scientist develops the following setup, shown in Figure 1 below, to study the charges of radioactive particles. A radioactive sample is placed into a lead box that has an open column such that the particles can only exit from one direction. A detector is placed in front of the opening. A metric ruler (centimeters (cm)), is aligned on the detector such that zero is directly in front of the opening of the column, with the positive values extending to the left and the negative values to the right. On the left side of the experimental setup, there is a device that generates a magnetic field that attracts positively charged particles and repels negatively charged particles.

 

                 Radioactivity_fig_1

                                                    Figure 1.

 

The device detects particles in three different places: alpha, α; beta, β; and gamma, γ; as labeled in Figure 1. The paths these particles take from the source of radioactivity are shown.

 

Experiment 2

A different scientist finds the following data, shown in Table 1, about the energies of the α, β, and γ particles by observing what kinds of materials through which the particles can pass. This scientist assumes that the ability of particles to pass through thicker and denser barriers is indicative of higher energy. Table 1 summarizes whether or not each type of particle was detected when each of the following barriers is placed between the radioactivity source and the detector. The paper and aluminum foil are both 1 millimeters thick, and the concrete wall is 1 meter thick.

 

                              Radioactivity_table_1

It is discovered that a certain element in the Earth's crust emits beta particles, and furthermore, that beta particles can cause cancer. Should architects building houses in the areas where this phenomenon is found in high abundance be mandated to build basements with concrete walls with a minimum thickness of one meter?

Possible Answers:

Yes, because beta particles are only stopped by concrete walls at least one meter thick.

No, because beta particles are negatively charged, and thus will bounce off the basement's external walls. 

No, because beta particles are not energetic enough to pass through an aluminum foil sheet. 

Yes, because there will be very large numbers of beta particles emitted from the Earth's crust in these areas.

Correct answer:

No, because beta particles are not energetic enough to pass through an aluminum foil sheet. 

Explanation:

Table 1 shows that a simple sheet of aluminum foil can deflect beta particles. Thus, we know that any basement walls will be sufficient to deflect beta particles, and extra measures to build thick walls would be a waste of materials.

Example Question #131 : Physics

Experiment 1

A scientist develops the following setup, shown in Figure 1 below, to study the charges of radioactive particles. A radioactive sample is placed into a lead box that has an open column such that the particles can only exit from one direction. A detector is placed in front of the opening. A metric ruler (centimeters (cm)), is aligned on the detector such that zero is directly in front of the opening of the column, with the positive values extending to the left and the negative values to the right. On the left side of the experimental setup, there is a device that generates a magnetic field that attracts positively charged particles and repels negatively charged particles.

 

                 Radioactivity_fig_1

                                                    Figure 1.

 

The device detects particles in three different places: alpha, α; beta, β; and gamma, γ; as labeled in Figure 1. The paths these particles take from the source of radioactivity are shown.

 

Experiment 2

A different scientist finds the following data, shown in Table 1, about the energies of the α, β, and γ particles by observing what kinds of materials through which the particles can pass. This scientist assumes that the ability of particles to pass through thicker and denser barriers is indicative of higher energy. Table 1 summarizes whether or not each type of particle was detected when each of the following barriers is placed between the radioactivity source and the detector. The paper and aluminum foil are both 1 millimeters thick, and the concrete wall is 1 meter thick.

 

                              Radioactivity_table_1

Based on Experiment 2, the scientist could conclude that the particles, in order of increasing energy, are __________.

Possible Answers:

α < β < γ

γ < α < β

β < α < γ

α < γ < β

Correct answer:

α < β < γ

Explanation:

In the description of Experiment 2, it is stated that it assumed that the thicker and denser the materials a particle can pass through, the higher the energy of the particle. Thus, since the alpha particle can be stopped even by a piece of paper, while the other two particles can pass through, it must have the lowest energy of the three particles measured. Secondly, the beta particle can be stopped by aluminum foil, while gamma particles pass through it, so the beta particle is second lowest in energy. Lastly, the gamma particles may only be stopped by a one-meter-thick concrete wall, so they are the highest in energy.

Example Question #132 : Physics

Experiment 1

A scientist develops the following setup, shown in Figure 1 below, to study the charges of radioactive particles. A radioactive sample is placed into a lead box that has an open column such that the particles can only exit from one direction. A detector is placed in front of the opening. A metric ruler (centimeters (cm)), is aligned on the detector such that zero is directly in front of the opening of the column, with the positive values extending to the left and the negative values to the right. On the left side of the experimental setup, there is a device that generates a magnetic field that attracts positively charged particles and repels negatively charged particles.

 

                 Radioactivity_fig_1

                                                    Figure 1.

 

The device detects particles in three different places: alpha, α; beta, β; and gamma, γ; as labeled in Figure 1. The paths these particles take from the source of radioactivity are shown.

 

Experiment 2

A different scientist finds the following data, shown in Table 1, about the energies of the α, β, and γ particles by observing what kinds of materials through which the particles can pass. This scientist assumes that the ability of particles to pass through thicker and denser barriers is indicative of higher energy. Table 1 summarizes whether or not each type of particle was detected when each of the following barriers is placed between the radioactivity source and the detector. The paper and aluminum foil are both 1 millimeters thick, and the concrete wall is 1 meter thick.

 

                              Radioactivity_table_1

A new type of radioactive material is discovered. A sample of it is placed into the lead chamber of the experimental setup described in Experiment 1. The detector detects radioactive particles at +1 cm. Which one of the following statements is true?

Possible Answers:

The material emits γ particles.

The material emits β particles.

None of these

The material emits α particles.

Correct answer:

None of these

Explanation:

Radioactivity sources that produce α particles will produce a signal at +2 cm, sources that produce β particles will produce a signal at –1 cm, and sources that produce γ particles will produce a signal at 0 cm. As no known signal occurs at +1 cm, it is clear that this source of radioactivity produces a fourth type of particle. 

Example Question #1251 : Act Science

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 students' hypotheses were correct, what might be a worthwhile question for them to study next?

Possible Answers:

What other properties of matter affect velocity of sound through a substance?

Does density affect the velocity of sound in substances other than those tested in Study 1?

Does the length of the sample used affect the velocity of sound through a substance?

What is the velocity of sound in water over 100°C?

Correct answer:

What other properties of matter affect velocity of sound through a substance?

Explanation:

If the velocity of sound through a substance is directly dependent upon the density of the substance, then that would mean increasing density should always result in increasing velocity. Because this is not the case (see "lead" in Table 1 and the increasing velocities as density decreases in Table 2), there must be another factor or multiple factors affecting the velocity of sound as it travels through a substance.

The students' correct hypotheses would account for the remaining answer choices, so these would require no further investigation.

Example Question #1252 : Act Science

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

Suppose a second group of students hypothesizes that the velocity of sound is inversely dependent upon the density of the substance through which the sound travels. Which study would best support their hypothesis and why?

Possible Answers:

Study 2, because velocity increases as density increases

Study 1, because velocity decreases as density decreases

Study 2, because velocity decreases as density increases

Study 1, because velocity decreases as density increases

Correct answer:

Study 2, because velocity decreases as density increases

Explanation:

In order for velocity to be inversely dependent upon density, one must increase as the other decreases. This is most consistent with the results of Study 2.

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