Chapter 1: Measurement PSCI 1421: Physical Science I Instructor Casquete UTPA Lecturer An Introduction to Physical Science Shipman/Wilson/Todd 12 th Edition

Chapter 1 Outline 1.1: What is Science? 1.2: The Scientific Method 1.3: Conversion 1.4: Significant Figure Choose the topic for next week Quiz

Physical Science Physics Chemistry Astronomy Meteorology Geology 3 Physical Science & Biological Science Natural Sciences

What is Science?

What Is Science? Student interaction

What is not Science? SPELL, REVENGE, BRUJERIA… Rancho Viejo, March 3, 1993 A 17 year young man was gunned down. Why? Pre-Conceived Ideas/Superstitions

What Is Science? Which of the following best describes “science”? A compendium of answers A set of rules about the natural world A methodology Exploration, curiosity; a compendium of questions Observation, experimentation Boring guys in white coats with nerdy senses of humor Science has bits of all these (esp. middle four) 7

Science = A Process for Change! Observations and Measurements (qualitative data) Hypothesis (a possible explanation) Experiments (Testing hypo) Theory (a well texted explanation) Law (describes a fundamental relatitionship of nature) 8 An ongoing cycle – the “scientific method” Scientific Method: The dynamic interplay between theory and experiment

Should we even pay attention, then? Ever higher precision pushes incomplete theories to their breaking points 9 Science is always on the move theories that long stood up to experiment are shot down But usually old theory is good enough to describe all experiments predating the new trouble making experiment Otherwise it would never have been adopted as a theory Result is enhanced understanding deeper appreciation/insight

Science also brings an Attitude 10 Scientists must accept their experimental findings even when they would like them to be different. They must strive to distinguish between what they see and what they wish to see, for scientists, like most people, have a vast capacity for fooling themselves.

Science also brings an Attitude Cont 11 People have always tended to adopt general rules, beliefs, creeds, ideas, and hypotheses without thoroughly questioning their validity and to retain them long after they have been shown to be meaningless, false, or at least questionable. The most widespread assumptions are often the least questioned. Most often, when an idea is adopted, particular attention is given to cases that seem to support it, while cases that seem to refute it are distorted, belittled, or ignored.

1.4 Standard Units and Systems of Units Like many other sciences, physics uses Système International d’Unités (SI) as its standard form of measurement.

Base Units Length Mass Time Meter (m) Kilogram (kg) Second (s)

1.6 Derived Units Formed from a combination of base units – endless possibilities Derived QuantityUnit Area (length) 2 m 2, cm 2, ft 2, etc Volume (length)m 3, cm 3, ft 3, etc Speed (length/time) m/s, cm/s, ft/s, etc

1.6 Derived Units, Cont… Formed from a combination of base units – endless possibilities Common example: force is typically measured in Newtons (N) 1 N = 1 kg·m/s 2

Conversion Factors Scientists often need to make comparison of units between the metric and British systems. We are going to relate one unit to another. What should we care about units? What happen when Scientists don’t agree with unit system?

Conversion Factors: Example 1 Convert 6.5 km to m First, we need to find a conversion factor that relates km and m. We should know that 1 km and 1000 m are equivalent (there are 1000 m in 1 km) We start with km, so km needs to cancel when we multiply. So, km needs to be in the denominator

Conversion Cont: Example 1 Multiply original measurement by conversion factor and cancel units.

Conversion : Example 2 Convert 3.5 hours to seconds If we don’t know how many seconds are in an hour, we’ll need more than one conversion factor in this problem

Example 3 Convert 40 km/h to mi/h 1 mi = Km

Your turn 1) 65 yd is equivalent to how many meters? 2) How many seconds are there in a day? 3) Convert 34 km/h to mi/h 1 yd = m 1 mi = Km

Significant Figures Reason we use these is to keep track of how precise a measurement is! See handout for Sig. Fig. rules Round off each of the following: 1) (three significant figures) = ) (two significant figures) 2) 0.083

We speak math here… Mathematics is the language of physics!

Recap: What is science? System Conversion Significant figures