Summer Assignment

Radius of the Earth
I'm here to help...
Click on "Contents" to Scroll to each section.
This summer you will begin your physics experience by collecting measurements for the purpose of calculating... THE RADIUS OF THE EARTH! Crazy, right? Well, get used to that. Physics is going to blow your mind :)
Please read this entire page right away. . . completing the project in June will be of great benefit.  This is a SUMMER assignment and must be submitted ONLINE no later than August 22nd - the last day of summer break, BEFORE the 1st day of school.  

How Long Will This Take?

Plan on spending about an hour doing each of the following to finish this project:
  • an hour reading up on the project; 
  • an hour planning where and when you will collect data, 
  • an hour collecting data; 
  • an hour on angle and radius calculations and 
  • an hour typing up and submitting your report.  
Feel free and encouraged 1) to submit your work sooner than the due date, 2) to work in groups (just make sure you collect your own data and do your own work), 3) and to ask lots of questions!  I'm here to help... 

Where Do I Start?

Carefully and thoroughly read the following link and use its procedure to collect data and make calculations. Measure Earth's Radius with a Stop Watch   Make sure you understand that "H" is a difference between "the height of your eyes from the ground when you are standing up" minus "the height of your eyes from the ground when you are lying down on your stomach supported  on your elbows."  
H = hstanding -  hlying down  This number is significantly less than your actual height.  Remember, you are in a science class, so measure in meters, NOT feet and inches!  
You will be performing two trials of the procedure found in the link above: once by observing the sun (either setting or rising) AND once by observing the moon (either setting or rising).   

Where Do I Collect Data?

The best time and location to collect data is... on the day of the summer solstice (June 21st) on the equator, looking over the ocean.  Okay, okay, you are NOT required or expected to leave central PA to collect your data, but the accuracy of your results will have a lot to do with where you choose to do so.  Watching the moon set behind a building, or a line of tall trees, or a mountain, is unacceptable and will substantially negatively affect your results.  Find a location where you have a view of the Earth's natural horizon and can see the sun and moon rise or set on that horizon.  Check out "farms" and "fields."  See photos below for help.

What Do I Hand In?

Use your Trinity Google Docs account ONLY, (NOT Microsoft Word,), and TYPE the following:
      • Title your document with your name and period you will take physics this year. 
      • The date and time you collected data for sun trial and moon trial.
      • A description of the location(s) from which your data was collected.  Describe what was along the horizon and what was obstructing your view (if nothing, then say so).
      • Your TWO measured eye heights (standing and lying down) in meters only.  (Can be the same for both trials) 
      • calculation for "H."
      • The Time (in seconds) between the rises or between the sets for each trial.
      • Explanation of error (put after all calculations)
Type or write: (show all work)
      • Calculations for the angle through which the Earth rotates.  With A representing the angle, start with this equation...
A  =  360o x  (time betw. rises or sets)/(86,400 seconds in a day) 
      • Use the equation below to calculate R, the radius of the Earth.  Simplify, then solve, then substitute LAST. Convert R's measurement to kilometers (km).   "A" is the same angle calculated above.
A = cos-1 [R / (R+H)]
cos A = R/(R+H)
(R+H) cos A = R
                 Distribute on left, then use basic algebra to put all of the terms with an "R" in them on the left 
                 and all of the other non-R terms on the right. Continue to solve for R.
      • Calculate the Percent Error (using the accepted value of 6371Km for the radius of the Earth)
% Error  =   100  x  lcalculated-acceptedl / accepted

Calculations MAY be hand written, BUT THEN MUST BE photographed/scanned, and inserted into your Google-doc, EVERYTHING else must be typed. 

Also include your own photo of the location(s) where you gathered your data from the sun AND the moon.  The photos should have a clear view of where you stood and the horizon you used and include the sun and then the moon in the photos, within minutes before they set or after they rise. 


Radius of the Earth 
Up to 20 points will be awarded for following directions. For example: use Google docs, submit project in correct Google Classroom, submit by the deadline, typing everything but calculations, etc.  The rest of the points will be accumulated as shown below.  
Up to 20 Points
Up to 19 Points
Up to 13 Points   
Clearly describes the location(s) where data was collected for both the sun and moon trials. Description includes the obstacles between the student and the horizon. Contains photographs that include a view of the surface on which the student stood and the horizon and the sun and moon.
Describes the location for both trials but is missing one or two components listed in the "Proficient" column.
Describes the location for only one trial and/or is missing multiple components listed in the "Proficient" column.
Data for 2 - eye heights (one standing and one lying down) measured in meters.
Data for a time for each trial measured in seconds.
Also include the date and time of data collection.  
Incorrect units
Incorrect units and/or missing data.
Complete calculations provided for the angle through which the Earth rotated, the Earth's radius, and the percent error for both trials
All work not shown
All work not shown and/or missing calculations
    Explanation of Error
Detailed and realistic explanation of error possibilities. Answers...
Why do my results differ from the accepted value?
What I could have done differently to obtain results closer to the accepted value?
Explanation of error lacks validity or detail or explanation of error does not answer questions in "Proficient" Column
Explanation of error lacks validity or detail and/or explanation of error does not answer questions in "Proficient" Column

How Do I Submit My Work?
Once you know what period you have physics, 

1) Click to "Register for a Google Group ==>
2) go to and sign up for your class with the appropriate code below.

1st Period:  5sh7ten      3rd Period:  8p5rvi      4th Period:  xb7et81    7th Period:  d8vymcv    9th Period:  va8kz54

The project must be submitted via Google Classroom on a Google Doc no later than your last day of summer break.