Real World Physics Chapter 1 PDF

Real World Physics Chapter 1 Introduction What is a Physical Quantity? Any property of matter that can be Measured is called a Physical Quantity (or simply a Quantity). Some Examples of Quantities Time Moment of a Force Electric Current Length Work...

Real World Physics Chapter 1 Introduction What is a Physical Quantity? Any property of matter that can be Measured is called a Physical Quantity (or simply a Quantity). Some Examples of Quantities Time Moment of a Force Electric Current Length Work Potential Difference Distance Energy Resistance Displacement Power Magnetic Flux Speed Temperature Magnetic Flux Density Velocity Frequency Activity of a Radioactive Source Acceleration Sound Intensity Mass Electric Charge Momentum Electric Field Strength Force Capacitance What is Measuring? When you Measure an amount of a quantity, you Compare that amount with a standard amount of the same quantity. This standard amount is called a Unit.  SI UNITS In 1960 scientists agreed to use a particular system of units. They called this system the International System of Units. Any unit of this system is called an SI unit. SI units will be used throughout your physics course. The five Basic Quantities and Basic Units needed for Leaving Cert. Physics  DERIVED UNITS The unit of every other quantity is called a Derived Unit because it can be written as a product or quotient of one or more Base Units. Examples of derived units: Physical Quantity Symbol Name of SI unit Symbol Area A square metre m2 Volume V cubic metre m3 Speed v or u metre per second m s-1 or m/s Density  kilogram per cubic metre kg m-3 or kg / m3 Sometimes a Unit is given the Name of a Scientist who made discoveries in the area of science where that unit often occurs. When this happens the unit symbol is written with a capital letter but the name of the unit is not.  USING SI UNITS When doing numerical problems ensure that: The value of each quantity is expressed in the correct SI unit before you start. When you calculate an answer you write it with the correct unit after it. Marks will be lost in exams if you don’t. A space is left between a number and a unit. e.g., A length of 5 metres is written as 5 m, not 5m In a Derived Unit a space is left between the symbols of the basic units from which it is made. e.g., the unit of speed is: m s-1 not ms-1 the unit of density is: kg m-3 not kgm-3 1 m3 = 1 million cm3 Common prefixes used for multiples and submultiples of SI units Multiple or Fraction Prefix Symbol 109 giga- G 106 mega- M 103 kilo- k 10-2 centi- c 10-3 milli- m 10-6 micro- μ 10-9 nano- n 10-12 pico- p