please review the information below .
Measurements of Length and Time
Objectives
To make basic measurements of length and time
To practice graphing using spreadsheet software and paper and pencil.
1. Length
· Estimate a 1-meter length by putting a pen or pencil at one end of a table and placing a second pen or pencil about one meter away from the first.
· Use the measuring tape or a ruler to measure the actual length of your 1 meter estimate.
· Record the length of your meter estimate.
· Calculate the percent error of your estimated meter from an actual meter.
2. Time
· Estimate a 30-s time period while someone else times you using a stopwatch. (If you do not have a partner, you can do this experiment by closing your eyes; start the stopwatch and stop it when you think 30 s have elapsed.)
· Record the actual time of your estimate.
· Calculate the percent error of the estimate from the actual time.
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Data Table 1: Estimation of various measurements |
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Measurement |
Estimated |
Actual |
% Error |
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Length (m) |
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Time (s) |
· In this exercise you will use your hand, a ruler or a measuring tape to measure lengths of objects. You will then compare the precision of these different methods.
Hand width (Measurement of your hand span) ________ cm_______ m
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Data Table 2: Measurement of width and height of a |
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Width (cm) |
Width (m) |
Height (cm) |
Height (m) |
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Ruler or meter tape |
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Hand unit* |
* hand units x hand width
– In this exercise you will use a stop watch (phone) and different cues to measure time.
· Measure a vertical height of 2 m from the floor up.
· Stand on a chair and hold a ball (marble) at the marked height in one hand and the stopwatch in the other hand.
· Start your stopwatch at the same instant you release the object and stop the timer when you see the object hit the floor.
· Repeat three times and calculate the average.
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Data Table 3: Time measurements using visual cues |
Drop time (S) |
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Trial 1 |
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Trial 2 |
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Trial 3 |
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Average |
**Ask one of your family member or a friend to help you for the next part.
· Let your Family member time you while you drop the ball – use verbal commands like “start” or “now” to synchronize the dropping and timing.
· Repeat 3 times, find the average drop time of the object.
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Data Table 4: Time measurements using auditory cues |
Drop time (s) |
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Trial 1 |
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Trial 2 |
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Trial 3 |
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Average |
– In Data table 5 include your measurements of round shaped objects around the house using string, ruler or meter tape
* At least
4 different round objects.
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Object |
Diameter D (m) |
Circumference C (m) |
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1 2 2 |
………………… m |
………………… m |
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2 |
………………… m |
………………… m |
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3 |
………………… m |
………………… m |
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4 |
………………… m |
………………… m |
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5 |
………………… m |
………………… m |
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6 |
………………… m |
………………… m |
Graphing data and calculation of π based on the values from
Data Table 5
· The relationship between the circumference and the diameter of a circle is: C=
π D
·
Plot C vs D, C- circumference on the Y axis and D- diameter on X axis
and include it here
. [All Graphs should be on Graphing Paper or EXCEL]
***Please pay attention the graph should be a line; use “best fit line” do not simply connect the points. Watch the video posted on ecampus if you are using EXCEL
Questions
1. What are the SI units for length, time, and mass?
2. Can you think of an occasion when it would be adequate to use your “hand” measurement?
3. Considering the exact time of 0.64 s for a ball to drop from h=2m which of the time measurements (tables 3 and 4) is more accurate?
4. How much is the slope of the graph generated from data table 5?
5. Calculate the
percentage error
using the slope value as the experimental value of “pi” and π = 3.1415 for the accepted value.
