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General Physics 1
Circular Motion
Siena College Fall 2010
Ferris Wheel Analysis
In this lab, you will analyze a movie of the famous Cyclops Ferris Wheel at Hershey Park
(this ride has since been replaced). Simply click on the movie to take data. Follow the
directions and answer the questions on a separate sheet.
1. Open Logger Pro, then go to File Open. In the first window, choose the file called
FerrisWheel.cmbl.
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2. The first thing that must be done is to calibrate our measurement tool (we need to tell
Logger Pro how to convert from pixels in the movie to meters). The diameter of the
Ferris wheel, which is shown on the first frame, can be used as the known length. It
is 16.98 meters. Note that this is the diameter of the inside wheel, not the outside edge
of the carts. Click on the ruler icon (#1 in the picture shown above). Then pick a point
on the rim of the wheel and click and drag across the diameter. In the window that
pops up, make sure you change the “known length” field to match the diameter of the
wheel.
3. Click on the icon #2 shown in the figure above. This will instruct the software to
leave a trail of markers at every location that you point the cursor to and click.
4. Center the cursor over a point on the wheel that you think you can keep track of,
perhaps between two of the carts (at the end of one of the spokes). We suggest that
you choose a point in the lower left-hand portion of the picture. This is because these
points will not be obstructed by anything as the frames advance. Click on the point on
the wheel that you have chosen. The movie will advance to the next frame and a
small dot should appear at the location you clicked on. Determine where the spot has
advanced to and click on it again. Collect as many data points as you can (until your
spot is obscured by something in the movie).
General Physics 1
Circular Motion
Siena College Fall 2012
Ferris Wheel Analysis
Analysis (Answer on a separate sheet of paper)
5. Based on the trail of circles left on the movie image, does the Ferris Wheel appear to
be rotating with a relatively constant speed? Explain your reasoning.
6. In Logger Pro look at the velocity in the x and y directions vs. time How do these
velocity components seem to be varying? Hint: the velocity components in circular
motion vary in a specific way. Try to figure out how they are varying (how do vx and
vy vary in your plots) and provide an explanation.
7. In addition to the x and y components of velocity that we looked at above, let’s
consider the magnitude of the total velocity of the wheel. In general, how does one
get the magnitude of the total velocity from vx and vy?
8. In Logger Pro, calculate the magnitude of the total velocity from the x and y
components. Produce a plot of this total speed vs. time. Is the magnitude of the total
velocity (speed) relatively constant? Does this imply that the acceleration of the point
you clicked on is zero?
9. What is the magnitude and direction of the centripetal acceleration of a passenger on
this Ferris Wheel at the highest point? What is the magnitude and direction of the
centripetal acceleration of a passenger on this Ferris Wheel at the lowest point?
10. What forces act on a person at the top of the Ferris wheel? (Note that the person is
upside down at the top. What forces act on a person at the bottom of the Ferris
Wheel? Draw free-body diagrams for the passenger at both the highest and
lowest points. Show the direction of the net acceleration off to the side of each of
the free-body diagrams.
11. Translate each of the two free body diagrams into an algebraic expression based on
Newton’s second law (F = ma). Make sure your signs (+/–) are consistent with the
directions of the forces and acceleration. In each case, calculate the normal force
exerted on a 65 kg passenger. Is the normal force less than, equal to, or greater than
the gravitational force (mg) on the person? This normal force is referred to as the
person’s “apparent weight.” This is how heavy a person actually “feels”. So at the
highest and lowest points, does a person feel heavier, lighter, or the same as they
would feel standing still?