1 / 15

Measurement

Explore the evolution of measurement from ancient methods to modern systems like the SI, and learn about precision, accuracy, estimation, errors, and measurement tools.

molivarez
Download Presentation

Measurement

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Measurement Predictions, Ch. 1, Activity 2

  2. Measurements • What form of measurement existed 2,000 years ago? • Parts of the body were originally used: • Palms • Hands (in use today) • Digits • Feet (in use today) • Cubit (still referenced today)

  3. Measurements • Circumference of the Earth was determined by Erathosthenes (276 – 195 B.C.) by comparing the noontime shadows in two different cities and determining the differing angle of the sun at each location • He assumed a spherical Earth

  4. SI System • Sytems International • Regulated by the International Bureau of Weights and Measures in France. • NIST (National Institute of Science and Technology in Maryland). • SI maintains the standards for: • Length (meter) • Time (second) • Mass (kilogram)

  5. Standard Units of Measurement • Meter (m): • Circa 1790 - Originally defined as the 1/10,000,000 of the distance between the North Pole and the Equator. • Circa 1890 - defined as the distance between two lines on a platinum-iridium bar. • In 1983 it was defined as the distance that light travels in a vacuum in 1/299792458 s.

  6. Measurement Error • Random error: • Error that occurs due to the inherent uncertainty in any measurement tool. • Error that is the result of the natural variability in any measurement. • Systematic error: • Error that occurs due to improperly reading or recording a measurement.

  7. Precision • Precision is a measure of the repeatability of a measurement. The smaller the variation in experimental results, the better the repeatability. • Precision can be improved by instruments that have high resolution or finer measurements. • e.g. A ruler with millimeter (mm) divisions has higher resolution than one with only centimeter (cm) divisions.

  8. Which group of data has better precision?

  9. Accuracy • How close are your measurements to a given standard? • Accuracy is a measure of the closeness of a body of experimental data to a given known value. • In the previous table, the data would be considered inaccurate if the true value was 15, whereas it would be considered accurate if the standard value was 12.

  10. Estimation • When a precise measurement is not necessary use an estimate. • An estimate relies on past experiences and good judgment. • A college football player has a mass of 100 kg. • Since 100 kg is about 220 lbs, this appears to be a good estimate. • A high school basketball player is 4 m tall. • 4 m is about 14 feet! Not a good estimate.

  11. Estimation • Your teacher works 1440 minutes every day. • That is every minute in 24 hours! • A poodle has a mass of 60kg • Not a toy poodle. Maybe a standard poodle. • Your classroom has a volume of 150m^3. • Not too far off • The distance across the school grounds is 1km. • Again, close.

  12. Precise Measurements • How would you record this measurement using a centimeter ruler? • 5.15 centimeters. • Measure to the smallest division + 0.5.

  13. Precision: What do you think? • An Olympic swimming pool is 50 m long. How precise do you think that is? • An oil tanker holds 5x10^6 barrels of oil. How precise is this? • A 2” x 4” piece of lumber is a standard size. How precise do you think this measurement is?

  14. Measurement tools • When would you use each of these? • Meterstick • Ruler • Measuring tape • Vernier caliper • Micrometer caliper

  15. Measurement • What does it mean to calibrate?

More Related