Activity: Order of Magnitude Exercise with Heartbeats and Grass Blades
All data and analysis for this activity will be written in your lab notebook.
 Always use pen in your lab notebook. If you make any mistakes, that’s okay!
Just cross off the mistake with a straight line like this or like this and re-write the
correct response.
 On the first page of your lab composition book, start a table of contents. There
should be a column for the lab/activity title and a column for the page numbers on
which the activity is found.
 For your first entry, use the title of this lab, and start on page 1
 Be sure to number the pages of your lab notebook. You can use both sides of the
paper, IF you can still read both sides of the page easily.
 Turn to page 1 in your lab notebook. At the top of the page, print the title of the
lab, the date on which you are completing it, and the name(s) of your partner(s). If
you work on a lab for a second day (like we will for this one), indicate in your lab
notebook when the second day of data began.
Part 1: Heartbeats
In your lab notebook, re-create the following data table:
Heartbeat Count for a 60.0 second time interval (beats)
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
With one partner timing, the other partner takes his/her pulse for 60 seconds. Do this a total
of 5 times. Each person should record his/her own pulse data.
Data Processing:
1. Determine your average number of heartbeats per minute
(show your work, include units!)
2. Estimate the average lifetime of a person (include units!): _______
3. Use this value, and your average pulse, to estimate the number of times your heart will
beat in a lifetime. Show your work using the factor-label method (template shown
below…you just need to fill in the blanks!)
[
_____heartbeats
_____minute
_____hour
_____day
_____year
]∗[
]∗[
]∗[
]∗[
]
1 𝑚𝑖𝑛𝑢𝑡𝑒
1 ℎ𝑜𝑢𝑟
1 𝑑𝑎𝑦
1 𝑦𝑒𝑎𝑟
1 𝑙𝑖𝑓𝑒𝑡𝑖𝑚𝑒
= ___________ ℎ𝑒𝑎𝑟𝑡𝑏𝑒𝑎𝑡𝑠⁄𝑙𝑖𝑓𝑒𝑡𝑖𝑚𝑒
4. Redo this calculation using ONLY ORDERS OF MAGNITUDE for each of the 5 values you
multiplied together. Discuss how your two answers compare.
Part 2: Grass blades
Question: Given that grass seed is typically sold in 15-pound bags, a landscaping company wants to
determine an approximate number of bags that would be necessary to completely seed a field the
size of a standard American Football field.
Your tasks:
1. Determine how many grass blades, approximately, would be in the desired field.
2. Determine approximately how many grass seeds would be present in a typical bag of grass
seed (15-lb bag)
3. Determine how many bags of seed the landscaper would require to seed the field.
Data Collection Procedure:
Task 1:
1. Cut a sizable square hole out of the note card provided
2. Just outside at the end of the hall, place the card on an area of grass.
3. Carefully count the number of grass blades within that square.
Task 2:
1. Get a small container of grass seeds from the bag at the front of the room
2. Determine the mass of the grass seeds you obtained
3. Count the number of grass seeds in your sample
Data Collection:
Dimensions of the hole:
Length = _________ cm
Mass of grass seeds in container = _____ g
Number of grass seeds in container =
Width = __________ cm
_____ seeds
# of grass blades: _______
Data Processing:
1.
Determine the area of your note card’s square hole.
2.
# grass blades in 1 m2: _______ record this value on the class data table
Show how you calculated this value:
3.
Calculate the average number of grass blades in a square meter based on the class data..
4.
Calculate approximately how many grass blades you would expect to find in the area the
size of the football field (120.0 yards long, 53.3 yards wide). Remember, there are 36 inches
per yard and 2.54 cm per inch.
5.
Calculate approximately how many 15-lb bags of grass seed would be needed by the
landscaper to seed the field.
6.
Repeat both calculations (#4 and #5) using only Orders of Magnitude for each value you used
in the calculations. Your final answer for each will now be in terms of OM rather than a count.
7.
Of the calculations using the data or the calculations using the Orders of Magnitudes, which do
you think is a better way to report the number of grass blades? The number of bags of seed?
Explain your reasoning.