This assignment is broken into three tasks, as indicated below:
1. Do the introductory_pendulum_experiment (Physics 121, 201, 231, 241 students only)
The first important system we use in first-semester physics is the pendulum. The pendulum is also important for second-semester students, for whom a knowledge of simple harmonic motion is essential to the second-semester study of waves.
The physics of the pendulum is very interesting and important, first-semester students won't fully understand the pendulum until near the end of the first semester. Most second-semester students will come to the course with this knowledge, but some first-semester courses do not fully cover simple harmonic motion and for students eoming from such courses this experiment will be valuable in its own right. Second-semester students are expected in any case to demonstrate their ability to communicate and analyze experimental data.
We therefore begin with this simple experiment, in which you make a pendulum by simply tying a string or thread to an object, and counting the number of times it swings back and forth in a minute. You will do this for nine different string lengths. The experiment is at the link introductory_pendulum_experiment. This experiment is predicted that it will take students an average of a couple of hours. However depending on experience, background and the speed with which various students do their work, the time required can vary widely from one student to another.
2. Do the Timer Program and First 'Seed' Question:
A convenient way to time multiple events is with the TIMER program. The program is simple to use and the instructions are self-explanatory. Click on the link and do as instructed: Using the Timer Program This exercise takes most students between 15 and 30 minutes.
Go to the form First 'Seed' Question (Physics 121, 201, 231, 241 students only), read the introduction and instructions, view the short videos, do your best to answer the questions (or ask questions of your own) and submit.
3. View and respond to videos of some fundamental systems
The videos listed below can be downloaded directly and played with QuickTime (if you can play YouTube, you can play these). If you wish you can save them to be replayed later. File sizes range from 1.6 to 5 megabytes. Average length of clips is about 25 seconds.
These videos show a few fundamental systems that represent a lot of what we study in first-year physics. Many labs in your course will be based on similar systems, which can be set up using items in your Initial Materials package. You should view these videos and consider the questions posed within them, as well as the questions that accompany the links in this document.
Physics II students will of course be on familiar ground with many of these questions, which will for them constitute a reminder and refresher. Some of the later videos are of systems that will not be studied until second-semester physics, but which can at least be observed by Physics I students/ Everyone can speculate freely in their answers.
Unless otherwise indicated, all physics students should observe these clips and think about their answers to these questions.
You should view the video clips below, and think about the associated questions. You will then be asked to submit your answer using the form Responses to Questions about Key Systems. Be sure to see the form for instructions before composing your answers.
The pendulum and its motion are almost universally studied in first-semester physics. For Physics I students this is a brief introduction to the pendulum. Physics II students will likely be familiar with the terminology and the behavior of the pendulum.
What do we mean by equilibrium, frequency, amplitude and period of a pendulum?
The pendulum and its motion are almost universally studied in first-semester physics. For Physics I students this is a brief introduction to the pendulum.
Do the period and frequency of a pendulum depend on its length? If so, how?
Objects accelerating down inclines are almost universally studied in first-semester physics, as are freely falling objects (e.g., the marble between the end of the incline and the table).
What measurable quantities change when we change the slope of the incline?
The position at which the marble first contacts the blue piece of foam (on which it ultimately lands) changes with the slope of the incline. If we continue increasing the slope of the incline, will this position keep changing, and how?
Rotational motion is in many ways as simple as straight-line motion. Rotational systems often keep moving longer (objects moving in straight lines tend to run into things), and they keep passing the same position, so in some ways they are easier to observe.
Through how many degrees do you estimate the straw rotated, and how long did it take to come to rest after the push? So on the average, through how many degrees per second was it rotating?
How long did it take to complete its last 180-degree rotation? Through how many degrees per second was it moving, on the average, during the last 180 degrees?
Are there measurements you could take to confirm the obvious fact that the system is slowing down?
Did the pendulum hit the wall before or after the dropped washer hit the table?
What could you change in order to make the two hit at the same instant? There are a number of answers to this question; try to think of as many as possible.
How close in time would the two events have to be before you would be unable to detect the difference?
This system exhibits many of the most important aspects of wave motion.
What observable quantities indicate increasing tension as the ends of the rubber band chain are gradually puller further and further apart?
Is there any indication that the rubber band on the right end of the chain is under greater or lesser tension than the rubber band on the left? Is there any indication that the rubber band in the middle is under greater or lesser tension than either of the ends? Given the rubber bands and paper clips, how could we investigate these questions?
This system, and similar systems, can be used to gain a great deal of insight into the behavior of fluids.
Does the water level in the cylinder decrease at a constant, an increasing or a decreasing rate as time goes on?
Does the horizontal distance traveled by the falling water stream change at a constant, an increasing or a decreasing rate?
Does the amount of water exiting the cylinder per second increase or decrease as time goes on? Does it increase or decrease at an increasing or decreasing rate?
What could we measure to determine the speed of the water as it exits the cylinder?
Does the speed of the water exiting the cylinder increase, decrease or remain the same as it falls?
(Physics II students only): Does the gravitational potential energy of the system change with time? If so, how?
How are the answers to the above questions related?
Everyone should observe the system, but only Physics II students are expected to attempt answers to the questions.
Does the stack have greater potential energy before being stacked or after, or is the potential energy the same for both?
Does the stack have greater kinetic energy before being stacked or after, or is the kinetic energy the same for both?
If we know the mass of a domino and its height relative to the tabletop, how do we find its gravitational potential energy?
If we know the mass of a domino and its velocity, how to we find its kinetic energy?
If a domino is removed from the top of the stack and placed on the tabletop, does the potential energy of the system change? If the entire stack, except for the bottom domino, is moved off the bottom domino and placed on the tabletop, does the potential energy of the system change? Which final state of the system has the greater potential energy?
Everyone should attempt to answer these questions, but this system is particularly relevant to Physics II students. Physics II students should of course try to work their knowledge of Physics I into their answers, but this is a complicated system and at this point all answers will be considered good answers.
The box shakes back and forth from left to right. The box is inclined so that the end away from the camera is higher than the end closer to the camera. So how is it that some of the beads manage to 'climb' toward the 'high' end?
What do you think is the average ratio of the number of beads in the 'upper half' of the box to the number in the 'lower half'?
There are 4 large beads, 4 small beads and 7 medium-sized beads in the box (call this a 4-4-7 proportion). What percent of the beads in the box are of each size? Do you think the beads that make it to the 'upper half' are in the same proportion? How could you obtain data to measure this?
Everyone should attempt to answer these questions, but this system is particularly relevant to Physics II students. Physics II students should of course try to work their knowledge of Physics I into their answers, but this is a complicated system and at this point all answers will be considered good answers.
If you look at the video frame-by-frame you can probably see the pulse as it propagates down the chain. It becomes harder to see as it reflects back toward the far end, and becomes almost completely obscured before it starts its second trip toward the camera. It's worth trying to trace the pulse.
The pulsing motion is gradually replaced by a simple back-and-forth motion of the chain. Why do you think this occurs?
Everyone should attempt to answer these questions, but this system is particularly relevant to Physics II students. Physics II students should of course try to work their knowledge of Physics I into their answers, but this is a complicated system and at this point all answers will be considered good answers.
The frequency of the back-and-forth motion of the chain decreases when the chain gets shorter and increases when the chain gets longer. Why do you think this happens?
As previously instructed, you will submit your answers using the form Responses to Questions about Key Systems. See the form for instructions before composing your answers.