Ms. Denzmore’s Physics Class DeBakey HSHP

What is physics? Physics is the study of the physical world. Consequently, there are many areas within physics…

My favorite area! Astrophysics: The physics of stars, galaxies, etc

Who needs math? YOU NEED MATH! In order to do well in physics, you’ll need to be proficient in algebra and some trigonometry and geometry Let’s review some basic info

Scientific Notation Why do we use scientific notation? To make very big and/or very small numbers easier to handle What is the average distance between the Sun and the Earth? 93,000,000 miles or 9.3 x 10 7 miles What is the average distance between the Sun and Pluto? 3,670,052,070 miles or 3.67 x 10 9 miles

How to write a number in scientific notation. 1. Put the decimal after the first non zero digit and drop the zeroes i.e. 93,000,000 becomes Multiply the coefficient by 10 i.e. 9.3 x To find the exponent, count the number of places from the decimal to the end of the number i.e. 9.3 x 10 7

Multiplying #s in Scientific Notation Rules for multiplication: 1) Multiply the coefficients 2) Add the exponents (base 10 remains !!!) Examples: (3 x 10 4 )(2 x10 5 )= 6 x 10 9 (5 x 10 3 )(6 x 10 3 )= 30 x 10 6 = 3.0 x 10 7 (3 x )(3 x )= 9 x 10 -6

Dividing #s in Scientific Notation Rules for division 1) Divide the coefficients 2) Subtract the exponents (base 10 remains) Examples: (6 x 10 5 )/(2 x10 2 )= 3 x 10 3 (8 x )/(4 x )= 2 x (2 x 10 3 )/(4 x )= 0.5 x = 5 x 10 10

Significant Figures Rules for determining sig figs: 1. All non-zero digits are significant 2. Leading zeros in decimal numbers are not significant 3. Zeros between nonzero numbers are significant 4. Trailing zeros in numbers without decimals are not significant...but if the number has a decimal, trailing zeros are significant.

How many sig figs?? Example 1: cm Answer: 4 sig figs Example 2: mm Answer: 1 sig fig Example 3: oz Answer: 3 sig figs Example 4: 50.8 mm Answer: 3 sig figs Example 5: 25,000 years Answer: 2 sig figs

Significant Rules When multiplying or dividing, the answer can only show as many significant digits as the measurement showing the least number of significant digits Example: 2.05 x x = Answer: 0.13

Significant Rules When adding or subtracting, the answer can only show as many decimal places as the measurement having the fewest number of decimal places Example: = Answer: 2.53

Mars Climate Orbiter Spacecraft launched in 1999 NASA lost contact with it 9 months later Investigation revealed that it burned up in the Martian atmostphere Cost: $193 million What happened?

It was the units!!  UNITS MATTER!! If you don’t use the correct units, your answer will be wrong. In physics, we use the metric system Mass (kilograms: kg) Time (seconds: s) Length (meters: m)

Metric powers of ten

The ones you must memorize!

Examples How many Hz are in 3250 GHz? G is Giga (10 9 ) 3250 GHz x 10 9 Hz 1 GHz 3.25 x Hz How many km are in 225 mm? 225 mm x m x 1 km 1 mm 10 3 m Or 225 mm x 1 m x 1 km 1000 mm 1000 m 2.25 x km

Be careful…some are tricky! How many cm 2 are in 400 m 2 ? When you have squared and cubic units, you must square or cube your conversion factors!! 400 m 2 x ( 1 cm) 2 = 400 x 1 cm 2 = 4 x 10 6 cm 2 (10 -2 m)

Another example How many cm 3 are in 625 km 3 ?