Presentation on theme: "1-1 What is Physics? What does Physics mean? "Physics" is from the Greek root physik (science of nature) and Latin physica (natural science). It’s."— Presentation transcript:
1-1 What is Physics? What does Physics mean? "Physics" is from the Greek root physik (science of nature) and Latin physica (natural science). It’s the scientific study of matter, energy, force, and motion, and the way they relate to each other. Studies how things work in the material universe. Chapter 1 The Science of Physics
http://www.youtube.com/ watch?v=AEIn3T6nDAo&f eature=youtu.be Video – The Big bang tv show – “what is Physics?”
Physics explains things that are very, very large. Physics explains things that are very, very small.
1-2 Measurements in Experiments Scientific Notation Extremely large or small numbers are expressed in powers of ten. 6.02 x 10 23 1.6 x 10 -19 Rules: When adding or subtracting numbers written in scientific notation exponents must be the same. Move the decimal point to the left you add one to the exponent, when moving decimal point to the right you subtract one from exponent. When dividing 2 numbers written in scientific notation subtract exponents. When multiplying 2 numbers – add exponents. Example: 4.25 x 10 7 + 2.25 x 10 8 2.68 x 10 8 or 26.8 x 10 7 are equal – same value
Scientists use the International System of Units, or SI. Common SI base Units: Length – meter (m) Mass – kilogram (kg) Time – second (s) Electric Current - ampere (A) Thermodynamic Temperature – kelvin (K) Amount of a substance - mole (mol) Derived Units – units that came from a combination of other units Example: Newton and speed 1 kg / m/s 2 and m/s
The Metric System I’m ten times better than the Standard system of measurement!”
Regardless of the unit, the entire metric system uses the same prefixes. Some common prefixes : giga = G x10 +9 or billions mega = M x10 +6 or millions kilo = k x10 +3 or thousands centi = c x10 -2 or hundredths milli = m x10 -3 or thousandths micro = x10 -6 or millionths nano = n x10 -9 or billionths pico = p x10 -12 or trillionths
To convert measurements use Dimensional Analysis by multiplying by a conversion factor: a factor equal to one. Example: To convert 56 m to km -- 56 m x 1 km = 0.056 km 1000 m Example: Convert 65 mph to km/hr 65 mi/hr x 1.61 km/hr 1 mi /hr = 104 km/hr Conversion factor
Accuracy and Precision Accuracy – describes how close a measurement is to the true value of the quantity measured. Precision – the exactness of a measurement Example: 45.052 m is more precise than 45.0 m Low Accuracy High Precision High Accuracy Low Precision High Accuracy High Precision
Significant Figures Used to show the precision of a measured quantity Include all digits that are actually measured plus one estimated digit. Rules: 1) All non zero numbers are significant 738 = 3 sig figs 12345 = 5 sig figs 2) Zeros located between non-zero digits are significant 2014 = 4 sig figs This measurement should be read as 4.95 cm. This measurement has 3 significant figures.
3) Trailing zeros (at the end) are significant only if the number contains a decimal point; otherwise they are insignificant (they don’t count) 1.00 = 3 sig figs 549000. = 6 sig figs 549000 = only 3 sig figs 4) Zeros to the left of the first nonzero digit are insignificant (they don’t count); they are only placeholders. 000.456 = 3 sig figs 0.052 = 2 sig figs
Rules for addition/subtraction problems The number of decimal places in the result equals the number of decimal places in the least precise measurement Example: 7.939 + 6.26 + 11.1 = 25.299 Answer = 3 sig figs 25.3 (rounded up) Rules for multiplication/division problems The number of sig figs in the result equals the number in the least precise measurement used in the calculation Example: (27.2 x 15.63) ÷ 1.846 = 230.3011918 Answer = 3 sig figs 230. (rounded down)
1-3 The Language of Physics Graphs and Charts Symbols In Physics there are 3 types of mathematical relationships that are most common. 1) linear relationship (or direct relationship) expressed by the equation y = mx + b where m is the slope and b is the y-intercept
2) Another relationship is the quadratic relationship. The equation is y = kx 2, where k is a constant.
3) The third equation is an inverse relationship, expressed by xy = k, where k is a constant.
Trigonometry will become important when we study vectors and parabolic motion Way to remember trig functions: “SOH CAH TOA”