Formal Lab Write Up
Use the information provided to write a formal lab. The experimental data as well
as the calculations have been done for you.
You might think that the Earth is round. Pictures of the Earth from space show that
Earth appears to be perfectly round and smooth. It is not perfectly round. How much
out of round is the Earth? Is the Earth or a globe more round? How smooth is the
earth? To us, Earth appears to have a highly irregular surface. Using model globes,
diagrams, and real Earth data, we can find out just how round and smooth the Earth is.
Hypothesis – Which do you think is rounder: a model classroom globe of the Earth a
diagram, or the real Earth? Which do you think is smoother: a globe of the earth, a
diagram of the Earth or the real Earth? Write a statement below about what you the
roundness and the smoothness of the Earth is.
This you do – Write out a hypothesis here!!
Part A – The Roundness of the Earth
Actual Earth Data:
Polar Diameter = 12,714 km
Equatorial Diameter = 12,756 km
Average Diameter = 12, 735 km
Height of Mt. Everest on Earth = 8.8 km
The ratio of the polar diameter to the equatorial diameter of a sphere is a measure of its
roundness:
PD
Polar Diameter
Roundness =
OR
R=
Equatorial Diameter
ED
Dividing the polar diameter by the equatorial diameter for a perfectly round sphere
would give a value of 1.0 since both diameters are equal. The farther from 1.0 the
actual computed ratio is, the less round the object is.
1. Using the Actual Earth data, record the polar and equatorial diameters of the
Earth in the data table for Roundness on the Report Sheet
2. Measure the polar and equatorial diameters of an Earth diagram below and
record in the data table
The measurements have
been done for you!!
Polar Diameter = 9.2 cm
cm
Equatorial Diameter = 9.4 cm
3. Measure the polar and equatorial diameters of an Earth globe (in cm to the
nearest tenth). Hint – find the polar and equatorial circumference, then calculate
the polar and equatorial diameters using the formula C = πd
4. Calculated the roundness ratio for the Earth and globe using the formula for
roundness.
5. Find the difference from 1.0 for the Earth, diagram and globe. Take the
roundness you recorded for each, and find the difference of that number from
1.0000.
6. Compare and rank the roundness of the Earth, diagram and globe from most
round to least round.
This has have been done
for you!!
REPORT SHEET
Roundness Table
Polar Diameter Equatorial
Diameter
Earth (km)
12,714 km
12,756 km
Roundness
(closeness to
1.0)
0.9967
Globe (cm)
30.3 cm
30.6 cm
0.9902
0.0098
Earth Diagram
(cm)
9.2 cm
9.4 cm
0.9787
0.0213
Roundness Comparison:
Most Round:
Middle:
Least Round:
Earth
Globe
Diagram
Calculations for the Roundness Ratio:
Earth:
R=
PD
ED
12,714 km
R = 12, 756 km
R = 0.0997
30.3 cm
R = 30.6 cm
R = 0.9902
9.2 cm
9.4 cm
R = 0.9782
Globe
PD
R=
ED
Diagram
PD
R=
ED
R=
Difference
from 1.0
0.0033
Part B – Smoothness of the Earth
The circle below represents a very round and very smooth Earth. Since you already
figured out how round the Erath should be, now you have to decide how smooth it
should be for its size.
How big do you think Mt Everest
Would be if Earth was as big as
this circle?
Draw a mountain the height you
think it should be on the circle
just above the arrow.
This has been done for
you!!
Now, we’ll go find out how close you were and how big the mountain should be for a
circle this size if the earth were this size.
A relief globe is a model that shows the relative height of its surface features, such as
mountains. So, where there is a mountain on earth, the globe sticks up a little to show
it. It is supposed to be a true scale model representing actual differences on earth. A
scale model is supposed to be exactly like the original in proportion, only bigger or
smaller in size.
That means that however many times you’d have to multiply the circle to make a real
earth, you’d have to multiply the mountain you drew the same number of times. Let’s
find out if that’s true.
First, determine how big the mountain actually should be on a circle the size of the
diagram. To do this, you use a proportion comparing the real object to the model:
Average Size of Real Object
Actual Size of Feature on Object
Average Size of Model
X
=
X is your unknown that will be the actual size the feature should be
Math Work:
12,735 km
10.1 cm
8.8 km =
X
This has been done for
you!!
12,735 X = 88.9
X = 0.0069 cm – this is the size the mountain should be
on diagram
Now, measure the size of the mountain you drew on the diagram:
0.4 cm
Was the mountain you drew too big or too small compared to what your proportion
showed it should be? Too Big
Calculate your percent error for your drawing:
% Error = Difference from Accepted Value
Accepted Value
% Error =
X 100
0.4 cm – 0.0069 cm
X 100
0.0069 cm
% Error = 5,697.1 %
Now, using the average of the diameters of your globe from the roundness chart,
calculate how big the mountain should be on the globe if the globe is true to scale:
12,735 km
8.8 km
30.5 cm
X
12,735 X = 268.4
X = 0.021 cm
How much should the mountain actually stick out? 0.021 cm
Measure how much the mountain really does stick up on the globe: 0.2 cm
Calculate the Percent Error of the globe mountain:
% Error = Difference from Accepted Value
Accepted Value
% Error =
0.2 cm – 0.21 cm
0.021 cm
X 100
X 100
% Error = 852.4 %
According to your percent error calculation, how many times too big is the mountain on
the globe? 8.5 times too big
Discussion Questions:
This you do!!
1. How does the Earth’s polar diameter compare to its equatorial diameter?
2. Is the Earth a perfect sphere? How does your data confirm your answer?
3. Using the roundness ratio calculated, which is more nearly a perfect sphere: the
Earth, the globe, or the diagram?
4. In terms of both roundness and smoothness, name an object which would be a
good model of the Earth. Explain your choice.
Conclusion: From the information determined in this lab, describe the roundness and
smoothness of the Earth. Use data from the lab.
This you do!!
Formal lab reports are examples of technical writing and are written in the third person
impersonal (ex.: The diameter was measured and recorded on the report sheet), not in
the first person (ex.: I measured and recorded the diameter on the report sheet).
The formal lab write up will provide specific information in a specific format. Please
follow the template below when writing your formal lab. The report should be type
written, but information such as calculations can be hand-written so long as they are
very neat and organized.
All headings are left justified
Title – give the lab an appropriate title based on what the lab is about
Purpose – Use the information provided to write a statement about what the goal of this
lab is.
Hypothesis – A short statement which is a prediction to be tested about the goal of the
experiment
Procedure – a brief outline summarizing the steps taken to conduct the experiment
• What did you do – report what happened, not give directions
• Only include relevant information
• Bullet the information
Data – include data tables showing the data collected during the experiment.
Calculations – Show all calculations – this can be hand written but NEAT
Results – summarize the data collected – what did the data and calculations mean.
Discussion – Answer any relevant questions using the data collected. Include the
answers to questions by turning the questions around in your response. This
discussion should be cohesive and organized, not simply a list of your answers to the
questions
Conclusion – Address the purpose of the lab – indicate what was determined and
summarize the results. Relate this to the hypothesis and state whether the hypothesis
was correct or not and why.
Formal Lab Write Up
Use the information provided to write a formal lab. The experimental data as well
as the calculations have been done for you.
You might think that the Earth is round. Pictures of the Earth from space show that
Earth appears to be perfectly round and smooth. It is not perfectly round. How much
out of round is the Earth? Is the Earth or a globe more round? How smooth is the
earth? To us, Earth appears to have a highly irregular surface. Using model globes,
diagrams, and real Earth data, we can find out just how round and smooth the Earth is.
Hypothesis – Which do you think is rounder: a model classroom globe of the Earth a
diagram, or the real Earth? Which do you think is smoother: a globe of the earth, a
diagram of the Earth or the real Earth? Write a statement below about what you the
roundness and the smoothness of the Earth is.
This you do – Write out a hypothesis here!!
Part A – The Roundness of the Earth
Actual Earth Data:
Polar Diameter = 12,714 km
Equatorial Diameter = 12,756 km
Average Diameter = 12, 735 km
Height of Mt. Everest on Earth = 8.8 km
The ratio of the polar diameter to the equatorial diameter of a sphere is a measure of its
roundness:
PD
Polar Diameter
Roundness =
OR
R=
Equatorial Diameter
ED
Dividing the polar diameter by the equatorial diameter for a perfectly round sphere
would give a value of 1.0 since both diameters are equal. The farther from 1.0 the
actual computed ratio is, the less round the object is.
1. Using the Actual Earth data, record the polar and equatorial diameters of the
Earth in the data table for Roundness on the Report Sheet
2. Measure the polar and equatorial diameters of an Earth diagram below and
record in the data table
The measurements have
been done for you!!
Polar Diameter = 9.2 cm
cm
Equatorial Diameter = 9.4 cm
3. Measure the polar and equatorial diameters of an Earth globe (in cm to the
nearest tenth). Hint – find the polar and equatorial circumference, then calculate
the polar and equatorial diameters using the formula C = πd
4. Calculated the roundness ratio for the Earth and globe using the formula for
roundness.
5. Find the difference from 1.0 for the Earth, diagram and globe. Take the
roundness you recorded for each, and find the difference of that number from
1.0000.
6. Compare and rank the roundness of the Earth, diagram and globe from most
round to least round.
This has have been done
for you!!
REPORT SHEET
Roundness Table
Polar Diameter Equatorial
Diameter
Earth (km)
12,714 km
12,756 km
Roundness
(closeness to
1.0)
0.9967
Globe (cm)
30.3 cm
30.6 cm
0.9902
0.0098
Earth Diagram
(cm)
9.2 cm
9.4 cm
0.9787
0.0213
Roundness Comparison:
Most Round:
Middle:
Least Round:
Earth
Globe
Diagram
Calculations for the Roundness Ratio:
Earth:
R=
PD
ED
12,714 km
R = 12, 756 km
R = 0.0997
30.3 cm
R = 30.6 cm
R = 0.9902
9.2 cm
9.4 cm
R = 0.9782
Globe
PD
R=
ED
Diagram
PD
R=
ED
R=
Difference
from 1.0
0.0033
Part B – Smoothness of the Earth
The circle below represents a very round and very smooth Earth. Since you already
figured out how round the Erath should be, now you have to decide how smooth it
should be for its size.
How big do you think Mt Everest
Would be if Earth was as big as
this circle?
Draw a mountain the height you
think it should be on the circle
just above the arrow.
This has been done for
you!!
Now, we’ll go find out how close you were and how big the mountain should be for a
circle this size if the earth were this size.
A relief globe is a model that shows the relative height of its surface features, such as
mountains. So, where there is a mountain on earth, the globe sticks up a little to show
it. It is supposed to be a true scale model representing actual differences on earth. A
scale model is supposed to be exactly like the original in proportion, only bigger or
smaller in size.
That means that however many times you’d have to multiply the circle to make a real
earth, you’d have to multiply the mountain you drew the same number of times. Let’s
find out if that’s true.
First, determine how big the mountain actually should be on a circle the size of the
diagram. To do this, you use a proportion comparing the real object to the model:
Average Size of Real Object
Actual Size of Feature on Object
Average Size of Model
X
=
X is your unknown that will be the actual size the feature should be
Math Work:
12,735 km
10.1 cm
8.8 km =
X
This has been done for
you!!
12,735 X = 88.9
X = 0.0069 cm – this is the size the mountain should be
on diagram
Now, measure the size of the mountain you drew on the diagram:
0.4 cm
Was the mountain you drew too big or too small compared to what your proportion
showed it should be? Too Big
Calculate your percent error for your drawing:
% Error = Difference from Accepted Value
Accepted Value
% Error =
X 100
0.4 cm – 0.0069 cm
X 100
0.0069 cm
% Error = 5,697.1 %
Now, using the average of the diameters of your globe from the roundness chart,
calculate how big the mountain should be on the globe if the globe is true to scale:
12,735 km
8.8 km
30.5 cm
X
12,735 X = 268.4
X = 0.021 cm
How much should the mountain actually stick out? 0.021 cm
Measure how much the mountain really does stick up on the globe: 0.2 cm
Calculate the Percent Error of the globe mountain:
% Error = Difference from Accepted Value
Accepted Value
% Error =
0.2 cm – 0.21 cm
0.021 cm
X 100
X 100
% Error = 852.4 %
According to your percent error calculation, how many times too big is the mountain on
the globe? 8.5 times too big
Discussion Questions:
This you do!!
1. How does the Earth’s polar diameter compare to its equatorial diameter?
2. Is the Earth a perfect sphere? How does your data confirm your answer?
3. Using the roundness ratio calculated, which is more nearly a perfect sphere: the
Earth, the globe, or the diagram?
4. In terms of both roundness and smoothness, name an object which would be a
good model of the Earth. Explain your choice.
Conclusion: From the information determined in this lab, describe the roundness and
smoothness of the Earth. Use data from the lab.
This you do!!
Formal lab reports are examples of technical writing and are written in the third person
impersonal (ex.: The diameter was measured and recorded on the report sheet), not in
the first person (ex.: I measured and recorded the diameter on the report sheet).
The formal lab write up will provide specific information in a specific format. Please
follow the template below when writing your formal lab. The report should be type
written, but information such as calculations can be hand-written so long as they are
very neat and organized.
All headings are left justified except the title and your name (do not use heading names
for the title and name)
Title – give the lab an appropriate title
based on what the lab is about
14 pt font, Bold
Your Name – centered below title, 12 pt font, standard (not bold)
Purpose – Use the information provided to write a statement about what the goal of this
lab is.
Hypothesis – A short statement which is a prediction to be tested about the goal of the
experiment
Procedure – a brief outline summarizing the steps taken to conduct the experiment
• What did you do – report what happened, not give directions
• Only include relevant information
• Bullet the information
Data – include data tables showing the data collected during the experiment.
Calculations – Show all calculations – this can be hand written but NEAT
Results – summarize the data collected – what did the data and calculations mean.
Discussion – Answer any relevant questions using the data collected. Include the
answers to questions by turning the questions around in your response. This
discussion should be cohesive and organized, not simply a list of your answers to the
questions
Conclusion – Address the purpose of the lab – indicate what was determined and
summarize the results. Relate this to the hypothesis and state whether the hypothesis
was correct or not and why.