Physics - Chapter 1 Lesson 2: Physics and Measurement Notes

LEARNING TARGET JOURNAL

 What is Physics?What can I do with Physics?What is the scientific method?What is the difference between SI Base Units from Derived Units?Why do we use prefixes with SI Units?

NOTES

• The scientific method is a common set of steps that are common to all good scientific investigations.

• The SI Units are divided into two classes
1. Base – units that cannot be calculated or formed from other units.
2. Derived – units that are created from multiplication or division of other units.

BASE UNITS

 Measured Quantity Quantity Variable(s) Unit Unit Symbol length ∆x, ∆y, L meter m mass m kilogram kg time t, ∆t second s electric current I (uppercase i) ampere A temperature T kelvin K luminous intensity Iv candela Cd amount of substance n mole mol

EXAMPLE 1 - Write the following measurements using the appropriate SI prefix using unit symbols and words.

 1000 metersSymbol:        Words: 0.001 ampsSymbol:        Words: 2,000,000 gramsSymbol:        Words: 0.000 000 003 secondsSymbol:        Words: 4,520,000,000 Joules (J)Symbol:        Words: 0.000 024 Coulombs (C)Symbol:        Words:

EXAMPLE 2 – Translate the following measurements using unit symbols into words.

 50 μm 62 Ps 10 nm 3.2 TA

EXAMPLE 3 – Return the measurement to its base one unit. Label the units as words, not symbols.

 1 hectogram 4 nanoamps 15 micrometers 17.11 gigabytes

EXAMPLE 3 – Return the measurement to its base unit. Label the units as symbols, not words.

 50 μA 15 cm 0.675 mg 14 MCd

HOMEWORK – Chapter 1 Concept Bank (Due Monday 12/14)

 Physics - Chapter 1 Lesson 3: Accuracy and Precision with Significant Figures Notes

LEARNING TARGET JOURNAL

 Define accuracy and precision.What are Significant Figures?I will identify the significant figures in a measurement.

NOTES

 Accuracy is how close a measured value is to the true value or accepted value.Precision is how close each measurement is to each other measurement.Precision can be increased by adding more graduations on the scale. Measurements can be made to one extra decimal place than the scale provides.Significant figures are those digits that contribute to the accuracy and precision of our measurements.The numbers 1-9 are significant. 0 is significant when:It shows precision after a decimal point.4.2300 (5 sig figs)It is trapped between other significant figures.2804 (4 sig figs)0 is not significant when it is used as a placeholder between the significant figures and the decimal pointHINT: If the 0 must be written when the number is in scientific notation, then it is significant.If the 0 is not necessary when writing the number in scientific notation, then it is not significant.

EXAMPLE 1 – Determine if the data is accurate, precise, neither accurate nor precise or both accurate and precise.

 Accepted Value: 9.81 Measured Data:9.80 ; 10.02 ; 11.14 ; 7.15 Accepted Value: 299,792,458 Measured Data:299,792,450 ; 299,792,460 ; 299,792,455 ; 299,792,465 Accepted Value: 101,325 Measured Data:10,325 ; 10,320 ;10,315 ; 10,425

EXAMPLE 2 – Find the length of the given item using the scale provided.

EXAMPLE 3 – Identify the number of significant figures in the given measurement.

 1234 km 0.0125 N 3.400 m 0.779 s 6800 mi 305.2 ± 0.1 kg

EXAMPLE 4 – Express the given measurement with the indicated number of significant figures.

 8.3144621 ; 3 sig figs 931.494061 MeV; 4 sig figs 939.565379 MeV; 5 sig figs

 Physics - Chapter 1 Lesson 4: Dimensional Analysis Notes

LEARNING TARGET JOURNAL

 I will perform calculations with significant figures.I will convert units of measure using Dimensional Analysis.VIDEOSWanda Sykes – Convert to Metric SystemWanda Sykes – Doctor and Fruit

NOTES

 The number of significant figures you keep in your answer when you add/subtract measurements, you keep to the least precise measurement.When you multiply/divide measurements, you keep the same number of digits as the measurement with the least amount of sig figs.When you do multiple operations, use the multiplication rule when you have reached your final answer!Dimensional Analysis is the process for converting units from system to system, or even within the same system.                Write down the given value with units.Create a fraction using a conversion factor by placing the units you want to change in the fraction so they divide, or cancel out.Multiply the fraction of values.Repeat as many times as necessary until the only units that are not cancelled out match the desired result.

EXAMPLE 1 – Perform the given operation(s). Show final answer with the appropriate number of significant figures.

 Find the sum of the measurements:756 g, 37.2 g, 0.83 g, and 2.5 g Find the quotient: 3.2 m ÷ 3.563 s Find the product:5.67 mm × π Perform the following:4.5  + (9.81 )(1.283 s)

EXAMPLE 2 – Perform the indicated conversions. REMEMBER TO USE SIG FIGS WITH YOUR FINAL ANSWERS.

 432 cm to m 6.20 mg to kg 39.37 in to m 75 mph to 121  to

HOMEWORK – Chapter 1 Online Review (Due 12/14)