Chapter 4
List several useful problem solving skills Deductive reasoning Deductive Inductive reasoning Inductive A three step problem solving approach, (ACE) Analyze Calculate Evaluate
Conversion Factors Must be constructed from equivalent measurements Example: 1 dollar equals 4 quarters, ($1 = 4 x 25 cents) Equal in value Example: 1 meter = 100 centimeters A small number of large items = a large number of small items The meter stick has 100 cm or 1000 millimeters or 10 decimeters All are valid and equivalent measurements 100cm/1meter converts from meters to cm 1 meter/100 cm converts from cm to meters
Dimensional Analysis is a way to analyze and solve problems using the UNITS or dimensions of the measurements If each person at a party will eat 2 hamburgers, how many will you need for 18 people? 36 HB 2 HB/1 person x 18 person = 36 HB If each HB has 2 pickles, how many will you need? 36 HB x 2 pickles/1 HB = 72 pickles If 1 jar of pickles has 110 pieces, how many HB could be made?
Multi Step Problems Miles to Feet to Yards: If you went 3.5 miles, how many yards is that? What you need to know: 1 mile = 5280 feet 1 yard = 3 feet How to convert, (the units miles and feet cancel) 3.5 miles x 5280 feet /1mile x 1yard/3 feet = ___ yards You get an answer in yards -> 6160 yards
Converting Complex Units Many measurements are expressed as a ratio of units, (miles per hour, Kilometers per second,…) Convert 10 mi/hr to km/sec, (the units of same color cancel) 10 mi/ hr x 1 km/.55 mi x 1 hr /60 min x 1 min / 60 sec= So you are left with units of km/sec The math is 10 x 1 x 1 x 1 /.55 x 60 x 60 = The answer is km/sec