PHYSICS BASICS

Science Measurements and Units

MEASUREMENTS

Measurements consist of a number and a unit.

Example

100 meters

the number of units

the unit

INTERNATIONAL SYSTEM OF UNITS (SI units) Developed for the sake of

consistency ease of understanding sharing data

BASE SI UNITS (standard units)

Measured quantity

DERIVED UNITS

Derived Units: Combinations of the 7 base units.

Examples Area (length x width) m x m = m2

Velocity (distance/time) = m/s

10 meters

5 meters50 m2

How to Measure? Know how to operate the measuring

instrument Which unit(s) is represented? What does each tick mark represent? Are there multiple scales? Did you zero out the instrument (if possible)

Be skilled and patient enough to measure with the greatest detail possible

What do the tick marks represent on a meter stick? What unit is represented by the

smallest tick mark on the meter stick?

m?

dm?

cm?

mm? *

What do the tick marks represent on a meter stick? What is the measurement?

In mm?

65 mm

In cm?

6.5 cm

In dm?

.65 dm

In m?

0.065 m?

ACCURACY

Accuracy is the extent to which a measurement approaches the true value.

Your Time:

2:05 pm

Actual Time:

2:10 pm

Your accuracy is off by 5 minutes

- The bull’s eye represents the true value.- The darts represent three separate measurements

accurate

less accurate

these darts show good accuracy

which paint ball mark is more accurate?

PRECISION

Precision is the degree of exactness of a measurement.

Based on the scale of the measuring instrument.

Smallest tick marks represent millimeters (mm)

PRECISION VS. ACCURACY

A—Good precision and accuracy

B—Some accuracy and poor precision

C—Good precision and poor accuracy

D—Poor precision and accuracy

A B C D

Discussion Question When shooting free throws, is it

better to be precise or accurate?

It’s better to be accurate.