This document provides instructions for several virtual physics experiments exploring concepts like Kepler's laws of planetary motion, fluid dynamics, phase transitions of water, and the ideal gas law. Students are directed to use Java applets from various websites to gather experimental data, make observations, and analyze their results. They are asked to prove Kepler's laws, determine if water behaves as an ideal or viscous fluid, map the phase diagram of water, and investigate relationships between pressure, volume and temperature in a gas model. The goal is for students to validate scientific theories and write lab reports discussing their findings.

1. Mechanics – Keplerian Motion
Web Sites:
http://astro.unl.edu/naap/pos/pos.html
Introduction:
During the last quarter of the 16
th
century, the Danish nobleman, Tycho Brahe, provided careful
observation of the planets over an extended period of time (20
years). He hoped to use his data to verify his own model of the
solar system, in which the sun orbited the earth, and all other
planets orbited the sun. At Brahe’s death in 1601, his assistant
Johannes Kepler inherited the data that Brahe had accumulated.
Kepler spent some 20 years analyzing this data, looking for
mathematical regularities. He came to the conclusion that the
ideal of circular orbits should be discarded and should be
replaced with elliptical orbits. Kepler summarized his laborious
study of planetary motion with the following three laws:
1. The planets move in elliptical orbits with the sun at one
focus.
2. A line from the sun to any planets sweeps out equal areas
in equal time.
3. The square of a planet's period is proportional to the cube
of the planet's mean
distance from the sun.
Instructions:
1.

2. Load up the Java applets from the websites shown above. You
may use only one of the websites, or both…whichever works
best for you!
2.
Your task is to “prove” Kepler’s 3 laws using data from these
two websites. Those are all of the instructions…very vague, but
you should be able to do it!
3.
Generating graphs would be a wonderful way of proving these
laws! Snapshots would be another wonderful way to prove
these laws!
4.
In your lab report, discuss your experimental data regarding
each of Kepler’s Laws.
5.
Finally, write the report with your favorite word processor or
text editor and submit it to the instructor.
Archimedes Principle
Web Site:
http://lectureonline.cl.msu.edu/~mmp/labs/labarch/lab.htm

3. Introduction:
In this lab you will devise your own method of measuring the
density of unknown materials. There are two substances of
different type in the lab to choose from. You will also measure
the density of alcohol.
Instructions:
1.
Load up the Java Lab from the web site shown above.
2.
Run the Java applet by clicking “JavaLab” button. (It will open
in a separate window).
3.
You can select the sample substance (1 or 2) by selecting it with
the radio buttons. The sample hangs from a beam that is
balanced on the pyramid shaped support in the middle. Above
the sample, there is a Newton-meter (to measure the force)
connected to the beam. However, the Newton-meter is not
calibrated, and so it will only show you if the net force is
upward or downward or close to 0. You can see this by the
position of the blue needle on the device. If the blue needle
points exactly upwards, then the force is close to 0, and its
deviation from the vertical is a measure for the force.
4.

4. You can generate a counter force that balances the weight of the
sample by shifting the counter-weight on the right side of the
beam left or right. This can be done by mouse-drag or using the
left and right arrow keys on your keyboard. The value of the
counter force is read out in the window in the upper right
corner. Each time you press the arrow keys the force changes by
0.1 N. If you hold the shift key down at the same time, you can
make fine adjustments (0.02 N steps).
5.
By balancing the counter force so that it exactly cancels the
weight of the sample, you can get the needle on the Newton-
meter to point exactly vertical. The indicated value of the
counter force is then the weight of the substance.
6.
Measure the weight of each substance in air, in water, and in
alcohol.
7.
Devise a formula to extract the densities of both substances and
that of alcohol as well as the volume of each substance.
Carefully write out the steps that lead you to your findings and
record your final answers. If you can, include a discussion of
the measurement uncertainties and possible errors in your
extracted numerical values.
(On the positive side: there are no spreadsheets to operate or
plots to produce for this report!)
8.
Finally, write the report with your favorite word processor or
text editor and email it (as email attachment) back to the

5. instructor.
Helpful hints and equations:
·
The density of water is 1 g/cm
3
= 1000 kg/m
3
·
Density = mass / volume:
r
= m / V
·
Weight in air = mass * gravitational acceleration: W
air
= m · g
·
Buoyant force = weight in air - weight in liquid =
r
liquid
· V · g
·
The volume displaced by the sample is the same in both water
and alcohol. If the glass beakers are shifted to the up position,
the samples are completely submerged.

6. ·
Assume the value of g = 9.8 m/s
2
.
Fluid Flow
Web Site:
http://lectureonline.cl.msu.edu/~mmp/labs/labflow/lab.htm
Introduction:
We want to know what law applies for water draining from a
cylindrical container. We can imagine two different scenarios:
1.
Flow of an ideal fluid: Here the rate of change in the height of
the liquid in the container will be proportional to the square
root of the height, and we arrive at the time dependence of the
height:
h(t) = h
o
- a · t + b · t
2

7. where a and b are two constants to be determined by
the experiment, and h
o
is
the beginning height. (This derivation uses
Bernoulli's Law.)
2. Flow of a viscous fluid: Here the rate of change in the
height of the liquid in the
container will be proportional to the height, and we arrive at
the time dependence
of the height:
h(t) = h
o
·
exp(- t /
t
)
where
t
is a constant to be determined by the experiment. (This
derivation uses
Poiseuille's Law and the pressure-depth relation.)
It is the purpose of this experiment to find out which of the two
scenarios describes this particular physical reality better.
If you want to preview a condensed version of what is going to
happen in this experiment, you can load either of these video
clips, the larger size, (280 kB, Sorenson compression) or
smaller size (176 kB, cinepak compression) versions are
available. The are recorded in time-lapse, with 3 seconds
between frames. Since they will play at 8 frames per second, the

8. roughly two minutes that it took to drain this container are
compressed to less than 5 seconds. (I didn’t have much luck
trying to load either clip, so I hope that if you want to look at
the preview, that you are more fortunate!)
Instructions:
1.
Load up the Java Lab from the web site shown above.
2.
Run the Java applet by clicking “JavaLab” button. (It will open
in a separate window).
3.
Digitize the height of the liquid column by clicking on the
upper limit of it. After each click, the mouse position is
recorded and the movie is advanced one frame. You should try
to devise a consistent strategy on where you click (left, right,
center, ...). If you make a mistake, click on the "Undo Pt."
button in the applet, and the last point will be erased.
Please Note: If you are using a phone line to perform
this experiment, then please keep in mind that it can take a
couple of seconds between two successive frames of the video
you are digitizing.
Please do not get impatient.
You can see when the next frame is ready for you from
observing the text area: as soon as the result of your previous
click is displayed, the next video frame is ready for processing.

9. 4.
You can display the points that you have already digitized
before by clicking on the "Plot y(x)" button. It will turn red and
show the points overlaid on the video. Clicking the same button
again will turn this feature off.
5.
You can also plot the trajectory as a function of time directly
within the applet by clicking on the "Plot h(t)" button. Clicking
on the "Digitize" button will bring you back to the data input
mode.
6.
The numerical data you have collected are displayed in the text
area on the right side of the applet. After you are done
digitizing all frames, please copy your data into your clipboard
and export them into your favorite spreadsheet or graphing
program. There, you can fit the above two functional
dependencies to your data and decide which one fits better.
7.
Now produce a plot with your graphing program or by screen-
capture of the applet.
8.
Finally, write the report with your favorite word processor or
text editor and submit is to the instructor.
Tips for Fluid flow lab:

10. You are trying to decide which law-Bernouilli's or
Poiseuille's-best describes the flow of water. Is water an ideal
fluid (Bernoulli's law) or a viscous fluid (Poiseuille's law)? To
determine which is true, gather your data and then plot it as
both a polynomial function (Bernoulli's) AND as an exponential
function (Poiseuille's). You then decide, by looking at the two
separate graphs you create, which one you think best fits your
data. If you think the polynomial best fits your data, then you
have determined that water is an ideal fluid. If you think the
exponential function best fits your data, then you have
determined that water is a viscous fluid. EITHER ONE MAY
BE SUPPORTED DEPENDENT ON YOUR DATA
Phase Transitions
Web Site:
http://lectureonline.cl.msu.edu/~mmp/labs/labphase/lab.htm
Introduction:
Here you can explore the phase diagram of water. We start the
experiment with an unknown quantity of ice at a temperature of
-50°C. By heating the sample and measuring the temperature
repeatedly, you can see the response of water in all of its phases
to heating. This experiment has two purposes:
1. To explore, measure, and plot the phase diagram of
water
2. To determine the mass of the unknown quantity of
water by comparing to the known values of the latent heats of
melting and boiling, or to the specific heat capacity of water.
Instructions:

11. 1.
Load up the Java Lab from the web site shown above.
2.
Run the Java applet by clicking “JavaLab” button. (It will open
in a separate window).
Please Note:
Each time you reload the applet, it will use a different quantity
of water. So please be sure to complete all of your
measurements before closing the applet window. However, you
can use the
START
and
STOP
buttons in the applet as often as you want and thus reset the
initial temperature and heat conditions without changing the
mass of the water.
3.
In order to conduct your experiment, you need to first select a
heating rate by clicking on one of the radio buttons on the
heater below the bottle. Please note that the faster the heating
rate you select, the larger the measurement errors will become.
However, the smaller the heating rate is, the longer the
experiment lasts. So you need to find a compromise that is
acceptable to you.
4.
As you add heat, the total heat inserted into the calorimeter
containing the unknown mass of water is displayed on the
heater. In addition, the temperature of the H

12. 2
0 rises, as indicated by the green bar on the thermometer. You
can measure the temperature by clicking on the thermometer at
the upper end of that green bar. The result of your temperature
measurement and heat measurement is then displayed in the text
area on the right. (The displayed values include the
measurement errors.) We recommend that you measure the
temperature very frequently, every few seconds.
5.
Once the enclosed quantity of H
2
0 has reached a temperature of approximately 170°C, the heater
shuts off automatically, and your run has ended.
6.
We suggest that you first perform a quick scan of the entire
phase diagram with the maximum heating rate. You should not
measure the temperature at this point, but just make rough notes
on the points where the temperature changes rapidly, and where
it stays roughly constant. Then you can make another run for
your measurements. (It is possible to adjust the heating rate
during a given measurement, too!)
7.
Now it is time to plot your results. You can either export the
data with copy and paste from the text area, or you can simply
use the plot button provided by the applet. Generate a plot by
using your favorite graphing program or by screen capture of
the applet, and include it into your lab report.
8.

13. Calculate the mass of the water at each condition:
·
Ice
·
Ice / Water Change of State
·
Water
·
Water / Steam Change of State
·
Steam
From the known values of the latent heats and specific heat
capacities of the different phases of H
2
0 you can figure out the total mass of H
2
0 contained in our calorimeter. Write this number down and
explain how you came up with your answer. Also, try to give an
estimate for the error in your answer.
9.
Finally, write the report with your favorite word processor or
text editor and submit is to the instructor.
Ideal Gas Law
Web Site:

14. http://www.phy.ntnu.edu.tw/java/idealGas/idealGas.html
Introduction:
This java applet shows a microscopic model for an ideal gas.
The pressure that a gas exerts on the walls of its container is a
consequence of the collisions of the gas molecules with the
walls. In this model:
1. The molecules obey Newton's law of motion.
2. The molecules move in all direction with equal probability.
3. There is no interaction between molecules (no collisions
between molecules).
4. The molecules undergo elastic collisions with the walls.
You can change the following parameters
1. N: Total number of molecules
2. P: The presure of the system
3. v: The velocity of each molecules.
4. The width of the container (Click near the boundary and
Drag the mouse)
The volume of the container is adjusted automatically according
to the above parameters.
The animation is suspended when you press the mouse button. It
is resumed when you release the button.
Instructions:
1.
Load up the Java Lab from the web site shown above.

15. 2.
Try to find out the relationship (inverse or direct) between the
total number of molecules (N) and the volume (V) by increasing
the number of molecules at least ten times. Start with the
following values: Particles = 100, Pressure = 50, and
Velocity = 100. Record the data, and plot a graph of your
results. Determine the relationship.
3.
Try to find out the relationship (inverse or direct) between the
pressure of the system (P) and the volume (V) by increasing the
pressure at least ten times. Start with the following values:
Particles = 1000, Pressure = 40, and Velocity = 100. Record
the data, and plot a graph of your results. Determine the
relationship.
4.
Try to find out the relationship (inverse or direct) between the
velocity of the molecules (v) and the volume (V) by increasing
the velocity of the molecules at least ten times. Start with the
following values: Particles = 300, Pressure = 50, and
Velocity = 50. Record the data, and plot a graph of your
results. Determine the relationship.
5.
Finally, write the report with your favorite word processor or
text editor and submit is to the instructor.