Measurement, Measurement

Measurement

100

The process of comparing something with a standard

Measurement

200

Basic quantities that are independent of one another (example: length - meter ; mass - kg; time - second; temperature - kelvin; etc.)

Fundamental quantities

300

Combination of fundamental quantities (ex. speed, density, work, power, energy, etc.)

Derived quantities

400

Refers to the closeness of a measured value to the expected or true value?

Accuracy

500

Unpredictable or inevitable changes during data measurements.

Random errors

Conversion

100

Convert 2 km to m

2km=2×1000=2000m

200

Convert 150 cm to m

150cm=100150=1.5m

300

Convert 3 hours to seconds

3h=3×60×60=10,800s

400

Convert 5 km² to m²

5km2=5×1,000,000=5,000,000m2

500

Convert 90 km/h to m/s

90km/h=90×36001000=25m/s

Accuracy and Precision

100

You measure the table 5 times and get: 2.10 m, 2.11 m, 2.09 m, 2.10 m, 2.11 m.

True value: 3m

Not accurate but precise

200

Give the mean: 1,2,3,4,5,6,7,8,9,10 

0+1+2+3+4+5+6+7+8+9+10=55

Mean time=55/11=5s  

300

A student measures the density of copper and gets 9.20 g/cm³. The accepted (true) density of copper is 8.96 g/cm³.

Find the percent error.

2.68%

400

Another student measures the density of copper in a different experiment and gets 8.80 g/cm³.

• Find the percent difference between the two students’ results (9.20 g/cm³ and 8.80 g/cm³).

4.44%

500

A student measures the length of a table five times. The true length is 2.00 m.

• Set A: 1.98 m, 2.01 m, 2.00 m, 2.02 m, 1.99 m

• Set B: 2.20 m, 2.21 m, 2.19 m, 2.20 m, 2.21 m

1. Which set of measurements is more accurate?

2. Which set of measurements is more precise?

1. accurate  SET A

2. precise  SET B