What is Physics?

Physics is the attempt to describe all of physical reality through mathematics. The view of the universe we start with is Reductionism (reducing the complexity of reality to a simpler form). The overwhelming complexity of the universe can be reduced to objects that are moving and interacting with each other.

Our base 10 number system Place value and powers of 10 Every place or digit in a number is one power of 10 different than the place on either side of that digit 10 x = 10 multiplied by itself x times 10 -x = 1/(10 multiplied by itself x times) 1 = 10 0 The metric system is based on powers of 10.

Metric Prefixes Important ones for us are listed on our formula sheet. Many more exist but are not commonly used. One centimetre is written as 1cm and means 1x10 -2 m or 0.01m

Scientific Notation A number written in scientific notation is expressed as the product of two factors. The first factor is between 1 and 10. The second factor is a power of ten. I prefer exponential notation to scientific notation. It is simpler. Exponential notation differs from scientific notation in that the first factor may be any number that is convenient. Example: How many metres is 500 mm? replace milli with so 500mm = 500x10 -3 m

Assigning numbers to things around us. A number by itself is meaningless. Common attachments to numbers to give the numbers meaning are units. Standard units QuantityUnit NameUnit Symbol Lengthmetrem Timeseconds Masskilogramkg

Other units are derived (created) through a combination of these standard units. Speed is length / time or m/s Volume is length cubed or m 3 Density is mass / volume or kg/m 3

Converting between units Sometimes we can do it in our heads Other times we need a procedure to follow. Here is the factor label method that works every time and is also used in chemistry and any other time there are conversions.

Factor Label Method The key idea here is that units are treated like algebra symbols – you can multiply them by each other, divide with them, and often cancel them out. There are ft in one mile, feet in one meter, and seconds in one hour. Convert 75.0 miles/hour to m/s.

Factor Label Steps 1.Write the quantity to be converted as a fraction with one and only one unit in the denominator and one and only one unit in the numerator. 2.Multiply the original quantity by as many conversion factors as necessary to change the original units into the desired units.

Conversion factors All conversion factors are equal to 1. Conversion factors are created by dividing both sides of a unit conversion equality by one side or the other. 1km=1000m is a unit conversion equality.

Factor Label Method The key idea here is that units are treated like algebra symbols – you can multiply them by each other, divide with them, and often cancel them out. There are ft in one mile, feet in one meter, and seconds in one hour. Convert 75.0 miles/hour to m/s.

Time for practice