# 2018 AP Physics 1 Free Response #4

TLDRIn this educational video, Alan from Bottle Stem Coach tackles AP Physics 2018's free response question four, focusing on wave motion. He explains how to determine the instantaneous velocity and acceleration of two points, P and Q, on a string during a wave's propagation. Alan demonstrates the concept of distance traveled versus displacement, showing that point P moves 32 centimeters over a period despite zero displacement. The video is designed to clarify these physics concepts with clear illustrations and step-by-step explanations, aiming to aid students in their exam preparation.

###### Takeaways

- π The video discusses a wave question from the AP Physics 2018 exam, focusing on the properties of a transverse wave traveling to the right along a string.
- π Alan, the coach, explains the task of drawing arrows to indicate the direction of instantaneous velocity for two dots, P and Q, on the string at a specific moment.
- π Dot P is at maximum displacement, and dot Q has zero displacement, indicating their positions relative to the wave's center.
- π’ The direction of the instantaneous velocity for dot P is upwards since it is at the peak of the wave and about to start moving downwards.
- π΄ For dot Q, the instantaneous velocity is zero because it is at the equilibrium position and is about to start moving upwards.
- π Alan clarifies that the instantaneous velocity (V) is zero for dot Q at the moment shown because it is transitioning from moving downwards to upwards.
- π The video also covers drawing arrows for the direction of instantaneous acceleration, noting that acceleration is zero at the point where velocity is maximum.
- π The coach demonstrates how to sketch the string's position at a time T equals Big T over four, which is a quarter of the wave's period.
- π Alan explains that for dot P, the distance traveled between times T equals 0 and T is 32 centimeters, despite the displacement being zero due to the wave's periodic nature.
- π The video provides a step-by-step guide on how to correctly represent the wave's position and the motion of the dots on the string, including the correct way to calculate distance traveled.
- π¨ Alan humorously comments on the quality of his drawing, suggesting that penmanship might not be a grading factor but accuracy in representation is.
- π The scoring guidelines are briefly mentioned, emphasizing the importance of accuracy in the representation of the wave's position and the numerical answer for the distance traveled.

###### Q & A

### What is the topic of the video?

-The video is about solving Free Response Question number four from the AP Physics 2018 exam, which is a wave question.

### What type of wave is being discussed in the video?

-The video discusses a transverse wave traveling to the right along a string.

### What is the significance of dots P and Q in the context of the video?

-Dots P and Q are points on the string that are used to illustrate the behavior of the wave at different positions and times.

### What is the meaning of maximum displacement in the context of dot P?

-Maximum displacement for dot P means that at the instant shown, dot P is at the peak of its motion, either at the highest or lowest point of its oscillation.

### Why does dot Q have zero displacement at the instant shown?

-Dot Q has zero displacement because it is at the equilibrium position, not moving away from the center, which is a point of rest in the wave's cycle.

### What is the direction of the instantaneous velocity of dot P at the instant it has maximum displacement?

-At the instant dot P has maximum displacement, its instantaneous velocity is zero because it is momentarily at rest before changing direction.

### What does the arrow drawn for dot Q indicate at the instant it has zero displacement?

-The arrow for dot Q indicates that it is about to move upward as it is at the equilibrium position and is starting to accelerate in the direction of the wave's propagation.

### What is the relationship between velocity and acceleration at the instant dot Q has zero velocity?

-At the instant dot Q has zero velocity, its acceleration is maximum because it is at the turning point where the direction of motion changes, indicating the start of a new phase of motion.

### What does the video explain about drawing the string at time T equals Big T over four?

-The video explains that at time T equals Big T over four, the string should be drawn as a mirror image of its original position, shifted over by one quarter of the wave's period.

### How does the video describe the position of dot P at time T equals Big T over four?

-The video describes that dot P, which does not move horizontally, will be in the same vertical position as at time zero, oscillating up and down.

### What is the total distance traveled by dot P between times T equals 0 and T?

-Dot P travels a total distance of 32 centimeters between times T equals 0 and T, which is the sum of its upward and downward movements during one complete oscillation.

###### Outlines

##### π AP Physics 2018 Free Response Question 4 Analysis

In this segment, Alan from Bottle Stem Coach discusses Free Response Question 4 from the 2018 AP Physics exam, which is a wave question. He explains how to approach the problem involving a transverse wave traveling to the right along a string with two dots labeled P and Q. At a certain instant, P is at maximum displacement, and Q has zero displacement. Alan instructs viewers to draw arrows indicating the instantaneous velocity of each dot, noting that P's velocity is zero as it is at the crest and not moving sideways. He also explains how to draw the direction of instantaneous acceleration, emphasizing that at the turning point, the velocity is zero, and acceleration is changing direction. Alan then guides through drawing the string's position at a time T equals one-fourth of the wave's period, illustrating the wave's progression and the position of dot P. He concludes by calculating the distance traveled by dot P from time zero to time T, emphasizing the difference between distance and displacement.

##### π Scoring Guidelines and Conclusion for AP Physics Question

Alan reviews the scoring guidelines for the AP Physics question, comparing his sketch with the correct picture provided in the guidelines. He confirms that his drawing aligns with the correct answer, showing the string's position shifted by one-quarter of a wavelength for point P. Alan also verifies that his numerical answer for the distance traveled by dot P, which is 32 centimeters, is correct. He encourages viewers to like, comment, or subscribe for more videos and hints at another free response question in the next video. Alan concludes the session by thanking the viewers and signing off.

###### Mindmap

###### Keywords

##### π‘AP Physics

##### π‘Free Response Question

##### π‘Transverse Wave

##### π‘Displacement

##### π‘Instantaneous Velocity

##### π‘Instantaneous Acceleration

##### π‘Period of the Wave

##### π‘Wavelength

##### π‘Distance Traveled

##### π‘Scoring Guidelines

###### Highlights

Alan introduces the AP Physics 2018 exam free response question number four, focusing on wave dynamics.

The problem involves a transverse wave traveling to the right along a string with marked dots P and Q.

Dot P is at maximum displacement, while Q has zero displacement, indicating their positions relative to the wave's center.

Instructions to draw arrows indicating the direction of instantaneous velocity for dots P and Q.

Explanation of why dot P's velocity is zero due to its position at the peak of the wave.

Dot Q's velocity is non-zero as it is not at the peak or trough of the wave.

Instructions to draw the direction of instantaneous acceleration for dots P and Q.

Dot P's acceleration is zero at the instant shown due to the transition from downward to upward motion.

Dot Q's acceleration is described in relation to its motion in the wave cycle.

Alan demonstrates how to sketch the string's position at time T equals a quarter of the wave's period.

The string's sketch is a mirror image shifted over a quarter of the wave, illustrating wave periodicity.

Alan explains how to determine the position of dot P at time T equals two, noting its vertical movement only.

Calculation of the distance traveled by dot P between times T equals 0 and T, emphasizing the difference between distance and displacement.

Dot P's total distance traveled is calculated as 32 centimeters, highlighting the wave's amplitude and period.

Scoring guidelines are reviewed, emphasizing the importance of correct diagram representation and numerical answers.

Alan concludes the video with a summary of the question's requirements and the correct numerical answer.

A call to action for viewers to comment, like, or subscribe for more educational content.

###### Transcripts

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