1 Outline

1
1 Outline

• Measurements Units
• Significant Figures
• Problem Solving
• Homework
• 6, 22, 29, 31, 45, 53, 68, 75.

2
SI Base Units

• meter (m)
• kilogram (kg)
• second (s, sec)
• ampere (A)
• kelvin (K)
• mole (mol)
• candela (cd)

3
Common Prefixes
0
Prefix Symbol Power of 10
giga G 109
mega M 106
kilo k 103
centi c 10-2
milli m 10-3
micro µ 10-6
nano n 10-9
4
Common Units

• mm 1000mm 1m
• cm 100cm 1m
• ft 3.28ft 1m
• mi 1mi 1609m
• gram 1000gram 1kg
• hour 1h 3600s

5
Unit Analysis

• calculation and comparison of units
• Ex. v at v m/s t s
• both sides of have same units
• m/s as
• m/s/s a

6
Dimensional Analysis

• units replaced by dimensions
• e.g. meter L, seconds T
• unit-independent
• e.g. velocity L/T

7
Unit Conversions Exs.
8
Significant Figures (s.f.)

• estimate of measurement precision
• trailing 0s count (3.00)
• leading 0s not counted (0.004)

1.56 3 s.f. 3.0/1.56 1.9
1.560 4 s.f. 3.0000/1.56 1.92
1.056 4 s.f.
12.001 5 s.f. 3.0 1.56 4.6
0.001 1 s.f. 3.0000 1.56 4.56
0.0010 2 s.f.
9
Problem Solving

• write key data as you read
• mark unknowns with ?
• double check each value
• use SI values, e.g. 5cm ? 0.05m
• sketch physical situation
• write equations
• solve, consider, read question again

10
Summary

• Unit and Dimensional Analysis
• Metric Prefixes -9 to 9
• Unit Conversions
• Problem Solving