PHYSICS BASICS Science Measurements and Units MEASUREMENTS n

PHYSICS BASICS Science Measurements and Units

MEASUREMENTS n Measurements consist of a number and a unit. n Example 100 meters the number of units the unit

INTERNATIONAL SYSTEM OF UNITS (SI units) n Developed for the sake of consistency n ease of understanding n sharing data n

BASE SI UNITS (standard units) Measured quantity

DERIVED UNITS Derived Units: Combinations of the 7 base units. n Examples n Area (length x width) m x m = m 2 n Velocity (distance/time) = m/s n 50 m 2 10 meters 5 meters

How to Measure? n Know how to operate the measuring instrument Which unit(s) is represented? n What does each tick mark represent? n Are there multiple scales? n Did you zero out the instrument (if possible) n n Be skilled and patient enough to measure with the greatest detail

What do the tick marks represent on a meter stick? n 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? n What is the measurement? In mm? 65 mm In cm? 6. 5 cm In dm? . 65 dm In m? 0. 065 m?

ACCURACY n Accuracy is the extent to which a measurement approaches the true value. Actual Time: 2: 10 pm Your Time: 2: 05 pm Your accuracy is off by 5 minutes

these darts show good accuracy accurate less accurate which paint ball mark is more accurate? - The bull’s eye represents the true value. - The darts represent three separate measurements

PRECISION n Precision is the degree of exactness of a measurement. n Based on the scale of the measuring instrument. Smallest tick marks represent millimeters (mm)

PRECISION VS. ACCURACY A n n B A—Good precision and accuracy B—Some accuracy and poor precision C n n D C—Good precision and poor accuracy D—Poor precision and accuracy

Discussion Question n When shooting free throws, is it better to be precise or accurate?

n It’s better to be accurate.