# Wright State University Lake Campus/2016-9/Phy1050/log/17sweenk

## 11/7/16 PHYSICS REPORT

For my research project, I chose to edit, review, and explain the first set of Test 1 questions that are available to the students for the How Things Work Physics course. Here, you will find notes on how to make test questions better and explanations of answers. I thought that students would more likely research and study questions if they had the information to solve the answers on the test right at their finger tips. So I compiled links and other data to directly reach the student so he or she can understand the concepts you are trying to teach. I hope that you will find this information I have gathered improves this course.

### Explanations of study guide questions:

How things work college course/Conceptual physics wikiquizzes/Velocity and acceleration:

1. When a table cloth is quickly pulled out from under dishes, they hardly move. This is because

• ANSWER: the cloth is accelerating for such a brief time that there is little motion
• WHY?: the others do not make sense. Use an educated guess when approaching this question. You can easily eliminate the answer about the cloth being “slippery.” This is not a scientific answer or reason. Choosing the correct answer makes the most sense. All you have to do is think about a magician and he or she pulls out the table cloth and it seems like the glasses and plates hardly even move.

2. A car is traveling west and slowing down. The acceleration is

• WHY?: The key words here are “slowing down.” The car is decelerating from the west and accelerating towards the east.

3. A car is traveling east and slowing down. The acceleration is

• WHY?: Same as number 2’s explanation but opposite. The car is decelerating from the east and accelerating towards the west.

4. A car is traveling east and speeding up. The acceleration is

• WHY?: The key words here are “speeding up.” Since the car is accelerating towards the east, the answer is clearly to the east.

5. If you toss a coin into the air, the acceleration on the way up is

• WHY?: The key word here is “acceleration.” Gravity plays a part in this answer. Since acceleration is where it is directed at, then going “down” is the correct answer since gravity comes into play at the end.

6. A car is traveling in a perfect circle at constant speed. If the car is headed north while turning west, the acceleration is

• WHY?: Pay attention to the word “acceleration” in this question. It is best to draw a picture for this one.

7. A car is traveling in a perfect circle at constant speed. If the car is headed north while turning east, the acceleration is

• WHY?: Pay attention to the word “acceleration” in this question. You are heading or rather, accelerating, towards the east. It is best to draw a picture for this one.

8. As the Moon circles Earth, the acceleration of the Moon is

• WHY?: Gravity draws the moon towards the Earth. In other words, the moon is acerbating towards the Earth.

9. If you toss a coin into the air, the acceleration on the way down is

• WHY?: Pay attention to the word “acceleration” in this question. Again, the coin is going down so it’s accelerating down.

10. If you toss a coin into the air, the acceleration while it as its highest point is

• CORRECTION TO WORDING OF ORIGINAL QUESTION: If you toss a coin into the air, the acceleration while at its highest point is
• WHY?: Pay attention to the word “acceleration” in this question. Again, the coin is going down so it’s accelerating down.

11. If you toss a coin into the air, the velocity on the way up is

• WHY?: This time, pay attention to the word “velocity” in this question. The velocity means the way in which an object is going so gravity does not play a part in determining where the coin is going. It’s basically the general direction in which the coin is headed.

12. If you toss a coin into the air, the velocity on the way down is

• WHY?: Pay attention to the word “velocity” in this question. Basically the general direction in which the coin is headed.

13. If you toss a coin into the air, the velocity while it as its highest point is

• WHY?: Pay attention to the word “velocity” in this question. It’s neither going up or down. It’s like at a standstill so it’s zero!

14. A car is headed due north and increasing its speed. It is also turning left because it is also traveling in a perfect circle. The acceleration vector points

• WHY?: Pay attention to the words “acceleration vector” in this question. It is best to draw a picture for this one.

15. A car is headed due north and increasing its speed. It is also turning right because it is also traveling in a perfect circle. The acceleration vector points

• WHY?: Pay attention to the words “velocity vector” and “increasing speed” in this question. It is best to draw a picture for this one.

16. A car is headed due north and increasing its speed. It is also turning left because it is also traveling in a perfect circle. The velocity vector points

• WHY?: Pay attention to the words “velocity vector” and “increasing speed” in this question. It is best to draw a picture for this one.

17. A car is headed due north and increasing its speed. It is also turning right because it is also traveling in a perfect circle. The velocity vector points

• WHY?: Pay attention to the words “velocity vector” and “increasing speed” in this question. It is best to draw a picture for this one.

18. A car is headed due north and decreasing its speed. It is also turning left because it is also traveling in a perfect circle. The acceleration vector points

• WHY?: Pay attention to the words “acceleration vector” and “decreasing speed” in this question. It is best to draw a picture for this one.

19. A car is headed due north and decreasing its speed. It is also turning right because it is also traveling in a perfect circle. The acceleration vector points

• WHY?: Pay attention to the words “acceleration vector” and “decreasing speed” in this question. It is best to draw a picture for this one.

How things work college course/Waves (Physics Classroom):

1. These two pulses will collide and produce

• WHY?: The two waves meet and the interference of the waves causes it to result I'm a larger, overall shape. This is sometime called constructive interference (http://www.physicsclassroom.com/class/waves/Lesson-3/Interference-of-Waves) which
• “is a type of interference that occurs at any location along the medium [line] where the two interfering waves have a displacement in the same direction.”

2. These two pulses will collide and produce

• WHY?: The pulses are not constructive interference and when they meet along the medium, they will displace each other. In other words, the waves will be destroyed.

3. These two pulses will collide and produce

• WHY?: This one is almost the same as question 1 and it has the same answer, why is that? Well, even though the waves look different, overall, the result is the same since the two waves are on the same side of the medium (line).

4. Two signals (dashed) add to a solid

• NOTE: Dr. Vandegrift, I propose that you remove the word “solid in your question because I think this word is a bit confusing. I find myself, as a student, becoming confused at which line to look at when you mention the word “solid” at the end.
• WHY?: An octave has a one to two ratio. By studying the picture you can tell that there is a pattern among the dashed waves. They alternate two to one, so this one represents an octave.

5. Two signals (dashed) add to a solid

• NOTE: Again, I propose that you remove the word “solid.” Refer to question 4 for an explanation for the change.
• WHY?: Dissonance is random sound waves, there is no pattern. By studying the given picture, you can tell that there is no evident pattern to it so this specific question is dissonance.

6. Two signals (dashed) add to a solid

• NOTE:Again, I propose that you remove the word “solid.” Refer to question 4 for an explanation for the change.
• WHY?: A fifth has the ratio of three to two. By studying the waves in the picture, you can see that there is one large wave to every two medium size waves.

7. Why don't we hear beats when two different notes on a piano are played at the same time?

• ANSWER: The beats happen so many times per second you can't hear them.
• WHY?: There are so many sounds going on that our brain cannot distinguish between the beats of TWO keys being played at the same time. We can hardly distinguish beats when playing one key, let alone two.

8. A tuning fork with a frequency of 440 Hz is played simultaneously with a tuning fork of 442 Hz. How many beats are heard in 10 seconds?

• WHY?: This is basic arithmetic. There is 2 Hz of a difference and if you multiply the 2 Hz per second by 10 seconds, you get 20.

9. If you start moving towards a source of sound, the pitch becomes

• WHY?: This is referred to as the Doppler Effect. There are many good examples of experiments done based on the Doppler Effect on YouTube. Basically, as you get closer to a sound, the pitch gets louder and vice versa.

10. If a source of sound is moving towards you, the pitch becomes

• WHY?: This is referred to as the Doppler Effect. There are many good examples of experiments done based on the Doppler Effect on YouTube. Basically, as the object gets closer you, the pitch gets louder and vice versa.

11. Why do rough walls give a concert hall a “fuller” sound, compared to smooth walls?

• ANSWER: The difference in path lengths creates more reverberation.
• WHY?: This has to do with reverberation. Reverberation is when sound waves are able to bounce off the walls at a faster pace than an echo. Auditoriums and concert halls use techniques to create reverberation so that the sound isn’t broken up like it is with an echo.

12. People don't usually perceive an echo when

• ANSWER: it arrives less than a tenth of a second after the original sound
• WHY?: People expect an echo to be heard shortly after a person speaks and have that sound repeat as it bounces off other stationary objects. When an echo arrives in a short amount of time, specifically less than a tenth of a second, it is much more difficult to perceive.

13. A dense rope is connected to a rope with less density (i.e. fewer kilograms per meter). If the rope is stretched and a wave is sent along high density rope,

• ANSWER: the low density rope supports a wave with a higher speed
• WHY?: Draw a picture or check out this link for a visual representation of this concept. Since the wave sent through the high density rope first, it makes sense that it can withstand the lower density rope.

14. What happens to the wavelength on a wave on a stretched string if the wave passes from lightweight (low density) region of the rope to a heavy (high density) rope?

• ANSWER: the wavelength gets longer
• WHY?: The wavelength is slowed down so it gets longer.

15. When a wave is reflected off a stationary barrier, the reflected wave

• ANSWER: has lower amplitude than the incident wave
• WHY?: Simply put, the wave’s amplitude is reduced once it hits a barrier. It’s somewhat like an echo, it is not quite as loud after hitting a barrier.

16. Comparing a typical church to a professional baseball stadium, the church is likely to have

• WHY?: The church is built to capture sound by reverberation. Imagine if a rock concert is held in a stadium. It will be hard to hear, right? That’s because of the sound echoing everywhere. The stadium was built to watch a game in action, not listen to a pastor or music in a church.

Physics equations/25-Geometric Optics/Q:image:

1. Shown is a corrective lens by a person who needs glasses. This ray diagram illustrates

• ANSWER: how a nearsighted person might see a distant object
• WHY?: The lens shown in the picture correct the sight of a nearsighted person because their eyes are not capable of making far away objects come at a parallel angle to their retina. The inverted lens enables nearsighted people to see further away by fixing the problem of the image coming into their retina parallel instead of unparalleled. Click on this link on to help you understand more about nearsightedness/farsightedness.

2. Shown is a corrective lens by a person who needs glasses. This ray diagram illustrates

• ANSWER: how a farsighted person might see an object that is too close for comfort
• WHY?: The lens shown in the picture correct the sight of a farsighted person because their eyes are not capable of making near objects come together. The oval shape of the lens magnifies the closer objects enabling farsighted people to read or see objects up close comfortably. Click on this link on to help you understand more about nearsightedness/farsightedness.

3. In optics, normal means

• ANSWER: perpendicular to the surface
• WHY?: The concept of normal comes from the Law of Reflection. Normal is perpendicular because it divides the incident and reflected rays into two equal angles.

4. The law of reflection applies to

• ANSWER: both flat and curved surfaces
• WHY?: The Law of Reflection states that light always reflects.

5. When light passes from air to glass

• ANSWER: it bends towards the normal
• WHY?: The best way to explain this is by replacing the word “glass” with “water” and “air” to “beach.” Imagine that there is a kid in the water and a lifeguard on the beach. The kid is drowning and needs help but the lifeguard needs to make the decision of which way is the fastest to get to the kid. Should he run straight into the water then paddle his way over to the kid at an angle? Or should he make the much wiser choice of spending the most amount of time on sand and the least amount in the water to get to the kid? The latter is the smartest and obvious choice. This is the same with light and the normal. This concept is called the Least Time Principle: “A ray of light will bend towards the normal when crossing the boundary from a medium in which it travels fast into a medium in which it travels slowly.”

6. When light passes from glass to air

• ANSWER: it bends away from the normal
• WHY?: Refer to the Least Time Principle of SFA: Slow to Fast, Away From Normal- “If a ray of light passes across the boundary from a material in which it travels slow into a material in which travels faster, then the light ray will bend away from the normal line.”

7. An important principle that allows fiber optics to work is

• WHY?: In fiber optics, the angle of the light when reflected hits a boundary, it completely reflects, otherwise referred to as total internal reflection.

8. The focal point is where

• ANSWER: rays meet if they were parallel to the optical axis before striking a lens
• WHY?: The words you need to pay the most attention to here are the “before striking a lens.” The focal point is only a considered a focal point when the parallel rays meet after passing through the lens.

Physics equations/25-Geometric Optics/Q:vision

1. Which lens has the shorter focal length?

• ANSWER: (The one picture with the star included in it.)
• WHY?: The question is asking specifically for the shorter focal length. Right away, you can eliminate the choice that says both have the same focal length because the pictures would have to be the same but they are not. The longest focal length picture does not even show its focal point because it’s so long. By process of elimination, it is easier to solve this question.

2. If this represents the eye looking at an object, where is this object?

• WHY?: Two of them are true, which ones? To begin with, the focal point is not short so the object has to be at a decent distance away. The choice “very far away” correctly summarizes this observation. The question also gives you the choice to choose “at infinity” which is entirely possible since we do not know where the focal point is. These are the two true answers.

3. After passing through a the lens of a camera or the eye, the focal point is defined as where the rays meet.

• NEED TO FIX WORDING OF QUESTION: After passing through the lens of a camera or the eye, the focal point is defined as where the rays meet.
• ANSWER: false but I disagree. This answer should be true because the definition of a focal point mentioned in the question above is in fact true. I researched this and came up with the same definition and explanations which do not match up to your answer.

4. Mr. Smith is gazing at something as shown in the figure to the left. Suppose he does not refocus, but attempts to stare at the star shown in the figures below. Which diagram depicts how the rays from the star would travel if he does not refocus?

• ANSWER: (the picture with the extended rays past the “eye”)
• WHY?: Mr. Smith goes from staring at an object a specific distance away to a much closer object, disorientating his eyes when he does not to blink or “refocus.” Since he goes from looking at a far away object to a closer one, the rays will criss cross each other and when drawn in a diagram, will extend beyond the eye before connecting.

How things work college course/Quantum mechanics timeline/Quiz

1. Excepting cases where where quantum jumps in energy are induced in another object (i.e., using only the uncertainty principle), which would NOT put a classical particle into the quantum regime?

• NEED TO FIX WORDING OF QUESTION: Excepting cases where quantum jumps in energy are induced in another object (i.e. using only the uncertainty principle), which would NOT put a classical particle into the quantum regime?
• WHY?: First of all, you need to know what the uncertainty principle is. (It’s basically a principle that states that the size of different atomic dimensions are controversial and therefore are in theory). (I must confess that I do not know how to fully explain this question so your help is much appreciated!)

2. What are the units of Plank's constant?

• NOTE: Plank is supposed to be spelled Planck.
• ANSWER: all of the above

3. What are the units of Plank's constant?

• NOTE: This is a repeat question. You must extract this from the test.

4. How would you describe Old Quantum Theory

• NEED TO FIX WORDING OF QUESTION: How would you describe the Old Quantum Theory
• ANSWER: neither complete nor self-consistent
• WHY?: Check out this link for the definition of the Old Quantum Theory!

5. The first paper that introduced quantum mechanics was the study of

• WHY?: In fact, a man named Thomas Young wrote this game changing paper which drove the further development of wave theory of light.

6. What are examples of energy?

• NOTE: I would change the answer “mgh where m is mass, g is gravity, and h is height” to PE=mgh just to make it look more presntable.
• ANSWER: all of the above

7. What are examples of energy?

• NOTE: Number seven is a repeat of number six. You need to remove this from the test bank.

8. What was Plank's understanding of the significance of his work on blackbody radiation?

• NOTE: Fix Plank’s to Planck’s.
• ANSWER: the thought it was some sort of mathematical trick
• WHY?: Refer to this Wikipedia link to Ultraviolet catastrophe and scroll down to the section titled “Historical inaccuracies.” There you will find a summary of Planck’s contribution to the study of blackbody radiation and his thoughts on the whole concept.

9. What was "spooky" about Taylor's 1909 experiment with wave interference?

• ANSWER: The light was so dim that only one photon at a time was near the slits.
• WHY?: Taylor was the first one to perform this experiment so he was disgruntled when he observed that only one particle goes through the slit at a time.

10. How does the Bohr atom differ from Newton's theory of planetary orbits?

• ANSWER: planets make elliptical orbits while the electron makes circular orbits
• WHY?: Elliptical orbits are best compared to the shape of ovals. The planets in our solar system have elliptical orbits where the planets are at times farther away from the sun or closer to it at different times. The Bohr atom uses circular orbits so that the electrons are at a consistent distance from the nucleus at all

times.