# A lab report for a high school physics class on the error of measurement.

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• Published: October 26, 2005

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Purpose:

The intention of this lab was to show how inaccurate and imprecise your measurements could be if you did not have the right measuring tools.

Procedure

1) Tennis Ball Diameter

A) circumference method

a) Take a piece of string and wrap it around the tennis ball in as straight of a path as possible

b) Place this string on a ruler and record measurement

c) The equation for diameter if a circle is

C=pi x d

B) average of two method

a) Take two tennis balls and place them side by side

b) Measure with a ruler the distance from one end of one tennis ball to the other end of the other tennis ball

c) Divide this distance by two to get the diameter of a tennis ball

C) Final averaging

a) Add up the diameters calculated from both the circumference and average method and divide by two to get the average diameter of a tennis ball

2) Diameter of a marble

A) Averaging method

a) Place four marbles side by side and measure the distance from end to end and divide by four to get the average of four marbles

b) Place three marbles side by side and measure the distance from end to end and divide by three to get the average of three marbles

c) Place two marbles side by side and measure the distance from end to end and divide by two to get the average of two marbles

d) measure one marble from side to side to get the diameter of one marble

e) Add up each of the calculated diameters and divide by four to get the average calculated diameter

3) Thickness of Copy Paper

A) Average method

a) count out 25 sheets of paper and measure the thickness using a ruler and divide by 25

b) count out 50 sheets of paper and measure the thickness with a ruler and divide by 50

c) count out 75 sheets of paper and measure the thickness using a ruler and divide by 75

d) add up all of the averages and divide by three to get the average calculated thickness

4) Height of school

A) Brick counting method

a) Measure the distance from the bottom of one brick to the bottom of the next brick.

b) Count the number of bricks from the bottom of the building to the top of the building

c) Multiply the number of bricks by the distance from the bottom of one brick to the bottom of the next brick

Data Tables

And

Measuring trials

Diameter of a marble

# of marbles Measured distance across Calculated diameter

4 6.45 1.16125

3 4.82 1.60666

2 3.18 1.59

1 1.61 1.61

Average diameter of a marble from all trials = 1.605

Thickness of paper

# of sheets Measured thickness Calculated thickness

50 .55 .011

25 .28 .0112

75 .84 .0168

Average thickness of paper = .013

Diameter of a tennis ball

Circumference of one tennis ball = 20.31

Calculated diameter of a tennis ball = 6.46

Diameter of two tennis balls = 12.89

Calculated diameter of a tennis ball = 6.445

Average diameter of a tennis ball = 6.45

Height of the high school

There were 121 bricks from the base of the school to the roof.

The height of one brick was measured to be 6.985cm

The calculated height of the school was 845.185cm

Error Analysis

Possible sources of error in this lab when measuring the diameter of the tennis balls were the tennis balls being "squished" while trying to get a measurement, the edge of the tennis ball not visible enough to be read from the ruler.

Possible sources of error when measuring the marble were not having a measuring tool precise enough to determine the edge of the marble.

Possible sources of error when measuring the thickness of the paper were miscounting the number of sheets of paper and not compressing the paper while measuring.

Possible sources of error while measuring the height of the school were the bricks not being consistently spaced and the bricks being hard to count near the top of the building

Conclusion:

Precision in a measurement is how many significant figures you measuring device will read to but that...