1.2: Activities
- Page ID
- 34437
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Things You Will Need
All you will need for this lab is this PhET simulator. Go ahead and run this simulator now in another window for use in the activities below.
Using the Simulator
This software simulates transverse wave motion along a one-dimensional medium (a string of beads). We'll start by configuring the simulator to start this lab...
- select the "Pulse" radio button in the upper-left corner
- leave the "Fixed End" radio button selected in the upper-right corner
- select the "Rulers" and "Timer" check boxes in the lower-right corner
- set the "Amplitude" equal to 1.00cm
- set the "Pulse Width" equal to 1.00s (the maximum)
- set "Damping" to "None" (the minimum)
- set "Tension" to "Low" (the minimum)
There are several features available that may help you with your tasks:
- The rulers and timer can be dragged-and-dropped around the screen for more accurate measuring (we will not need the vertical ruler, however).
- The "Slow Motion" radio button may come in handy if the wave is moving too fast for your purposes.
- You can set the apparatus so that the timer starts at the same moment as the pulse as follows:
- From a fresh restart, press the pause simulation button
(this will reveal the play simulation button
).
- Press the start timer button
(this will reveal the stop timer button
). Notice that the timer does not start with this click.
- Now clicking the pulse button will start the simulation, initiating a pulse and starting the timer at the same time.
- From a fresh restart, press the pause simulation button
- Pausing the simulation at any moment allows for easy length measurements and time stamps.
- You may want to advance the wave incrementally, to make measurements easier. You can step the simulator from a paused state using the step simulator button
.
A Simple Observation
We'll start the experiment with nothing more than an observation:
- Describe a feature that distinguishes the reflection of a wave pulse (a bump in the spring) off a fixed end from a reflection off a loose end.
- Does this reflection rule apply to waves that are more complicated than a simple bump? (You can switch the mode to "Manual" for this.) Provide a basic before/after reflection sketch (please don't submit a picture or a screen capture) of a wave you tried in the simulator that demonstrates your answer.
Computing the Tension
Playing with the tension slide bar reveals that there are only three settings – the "Low" and "High" labeled, and one unmarked setting between them. One might be inclined to assume that these are evenly-spaced (i.e. that the middle setting is the average of the low and high tensions), but it is dangerous to do so when the settings are not labeled. Your task will be to actually calculate the tension in the string for each of these three settings. You do this using measurements on the ruler and timer for a simulated pulse that you generate, as well as the following piece of data not available from the simulator:
every bead has a mass of 0.10 grams
- Use what you know about the physics of waves on strings to compute the three tensions (yes, they are very small numbers).
- Are the three tension settings evenly-spaced? That is, is the increase in tension from "Low" to the middle setting the same as the increase from the middle setting to "High"? If not, can you discern any pattern to these two jumps?
Lab Report
Download, print, and complete this document, then upload your lab report to Canvas. [If you don't have a printer, then two other options are to edit the pdf directly on a computer, or create a facsimile of the lab report format by hand.]