2. Chapter 2: Measurement and Units  2.1 Space and Time  2.2 Mass, Matter, and Atoms  2.3 Experiments and Data

3. Chapter 2 Objectives  Express lengths in metric and English units.  Convert measurements and calculated quantities between different units.  Calculate the surface area and volume of simple shapes and solids.  Work with time intervals in hours, minutes, and seconds.  Describe two effects you feel every day that are created by mass.  Describe the mass of objects in grams and kilograms.  Use scientific notation to represent large and small numbers.  Design a controlled experiment.  Create and use a graphical model based on data.

4. Chapter 2 Vocabulary  element  English system  experimental variable  exponent  friction  gas  graph  mixture  plasma  precision  procedure  scientific notation  SI system  solid  graphical model  independent variable  inertia  length  liquid  mass  metric system  speed  surface area  time interval  variable  volume  weight  x-axis  y-axis

5. Inv 2.1 Distance and Length Investigation Key Question: How do we accurately communicate length and distance?

6. 2.1 Space and Time  Space in physics means the three dimensions of up-down, left-right, and front-back.  The three dimensions of space are described with length units, such as meters, inches, and feet.  Time provides another dimension for describing when something occurs.

7. 2.1 Thinking about distance  Measurement — is a quantity and a unit  Distance —is the amount of space between two points —is measured in units of length

8. 2.1 Two common systems of units  Science problem solving requires both: —Metric or S.I. system —English system

9. 2.1 Two common systems of length  Almost all fields of science use metric units.  They make calculations easier because the units are based on factors of ten.

10.  It is often necessary to take a measurement in one unit and convert it into a different unit using conversion factors. 2.1 Converting from one unit to another

11.  You are asked for the distance in meters (m).  You are given the distance in yards (yds).  Relationship: 1 yard= 3 feet  100 yds x 3 ft x 0.3048 m = 91.4 m 1 yd 1 ft Converting length in yards to meters A football field is 100 yards long. What is this distance expressed in meters?

12. 2.1 Time  Two ways to think about time: —What time is it?  11:52 a.m. on March 12, 2010 —How much time has passed?  2 hr: 22 min: 42 sec.  A quantity of time is often called a time interval.

13. 2.1 How is time measured?

14.  You are asked for time in seconds.  You are given a time interval in mixed units. 1 hour = 3,600 sec 1 minute = 60 sec  Do the conversion: 1 hour = 3,600 sec 26 minutes = 26 × 60 = 1,560 sec  Add all the seconds: t = 3,600 + 1,560 + 31.25 = 5,191.25 sec Converting a mixed time to seconds How many seconds are in 1 hour, 26 minutes, and 31.25 seconds?

15. 2.1 Time scales in physics  Events in the universe happen over a huge range of time intervals.  In many experiments, you will be observing how things change with time.

16. Chapter 2: Measurement and Units  2.1 Space and Time  2.2 Mass, Matter, and Atoms  2.3 Experiments and Data

17. Inv 2.2 Time Investigation Key Question: How do we measure and describe time?

18. 2.2 Mass, Matter, and Atoms  Mass —is the amount of “stuff” an object contains.  Two effects mass has on matter: —Weight  is the force of the Earth’s gravity pulling down.  Gravity acts on an object’s mass. —Inertia  is the tendency of an object to resist changes in motion.  Inertia comes from mass.

19. 2.2 Measuring mass  Kilogram —is the mass of 1 liter of water or 1,000 cubic centimeters of water.

20. 2.2 Very large and very small numbers  Because physics covers such a wide range of values for length, time, and mass you will need a method of working with large and small numbers.  In scientific notation, numbers are written as a value between 1 and 10, multiplied by a power of 10 called the exponent.

22. 2.2 Matter and atoms  A single atom is about 10 -10 meters in diameter.  Aluminum foil is thin but still more than 200,000 atoms thick.  Whether matter is a solid, liquid, or gas depends on how the atoms are organized.

23. 2.2 Matter and atoms  Solids - Atoms in a solid stay together because the energy per atom is too low to break the bonds between atoms.  Liquids - Liquids flow because atoms have enough energy to move around by temporarily breaking and reforming bonds with neighboring atoms.  Gases - Gas atoms have enough energy to completely break bonds with each other.  Plasma - In plasma, matter becomes ionized as electrons are broken loose from atoms.

24. 2.2 The diversity of matter  There is an incredible diversity of matter around you.  This diversity comes from combining elements into compounds, then compounds into mixtures of compounds.

25. 2.2 The diversity of matter  Each type of matter is called an element.  Each element has is own properties, such as mass and the ability to combine with other elements.  There are about 92 different types of atoms in ordinary matter.

26. 2.2 The diversity of matter  A compound is a substance that contains two or more different elements bonded together.  Water is an example of a compound.  If you could look at water with a powerful atomic microscope you would find each particle of water is made from one oxygen atom and two hydrogen atoms.

27. 2.2 The diversity of matter  Another compound, glucose, is a sugar in food.  A single glucose molecule is made of carbon, oxygen, and hydrogen atoms.

28. 2.2 Matter and atoms  The matter you normally experience is made of mixtures of compounds.  Wood is a mixture that contains water and more than 100 other compounds.

29. Chapter 2: Measurement and Units  2.1 Space and Time  2.2 Mass, Matter, and Atoms  2.3 Experiments and Data

30. Inv 2.3 Matter and Mass Investigation Key Question: How is mass described?

31. 2.3 Experiments and Data  Data are the measurements and calculations that you make during the experiment.  Things you measure in experiments are fundamental quantities.  Derived quantities can be measured but are often calculated from things you originally measured.

32. 2.3 Speed  Speed —is a derived quantity calculated from measurements of distance and time.  Other derived quantities include frequency, density, acceleration, intensity, and energy.  Each of these units can be broken down into combinations of the fundamental units of length, mass, and time.

33.  You are asked for speed in mi/h.  You are given speed in cm/s.  Relationships: —speed = distance ÷ time —1 hour = 3,600 s —1 mile = 1,609 m —1 meter = 100 cm Converting a speed from cm/s to mi/h  A car on a ramp is measured to go 45 cm in 1.5 s. What is the speed in miles per hour? 4.

34. 2.3 Area and volume  A solid object has surface area as well as volume.  Surface area —is the measurement of the extent of an object’s surface or area without including its thickness.

35. 2.3 Area and volume  Volume —is a measure of the space occupied by an object.

36.  You are asked for surface area and volume.  You are given the radius.  Relationships: area: A = 4π r 2 ; volume: V = (4/3)π r 3  Solve: Surface area Volume A= 4(3.14)(12.5) 2 = 1,963 cm 2 V= 4 (3.14)(12.5) 3 8,181 cm) 3 Calculating area and volume A basketball has a radius of 12.5 cm. Calculate the surface area and volume of the ball.

37. 2.3 Density  Density describes how much mass is in a given volume of a material.  The units of density are mass divided by volume.  Identically-sized cubes of iron, polyethylene, and glass contain different amount of mass.

38. 2.3 Density  Solids range in density from cork, with a density of 120 kg/m 3, to platinum, a precious metal with a density of 21,500 kg/m 3.

39. 2.3 Accuracy and precision  Accuracy —is the quality of being exact and free from error. —is how close a measurement is to the true value.  Precision —means how small a difference a measurement can show.

40. 2.3 Variables and relationships  Factors that affect the results of an experiment are called variables.  The science of physics can be thought of as “the search for the relationships between all the variables that describe everything.”  To learn about something specific in nature, scientists instead select a small set of related variables and define it as a system.

41. 2.3 Variables for a car on a ramp

42. 2.3 Experimental design  We do experiments to find out what happens when we change a variable.  The variable that is changed is called the experimental variable.  The variables that are kept the same are called the control variables.  When you change one variable and control all of the others, we call it a controlled experiment.  Controlled experiments are the best way to get reliable data.

43. 2.3 Experimental design  The procedure is a collection of all the techniques you use to do an experiment.  Your experimental technique is how you actually do the experiment.  Each repetition of the experiment is called a trial.

44. 2.3 Graphical data  A graph shows how two variables are related.  By convention, graphs are drawn a certain way.  The dependent variable goes on the y-axis which is vertical.  The independent variable goes on the horizontal or x-axis.

45. 2.3 Graphical models  A graph is a form of a mathematical model because it shows the connection between two variables.  A graphical model uses a graph to make predictions based on the relationship between the variables on the x- and y-axes.

46. 2.3 Graphical models

47. 2.3 How to make a graph  Decide what to put on the x and y axes.  Make a scale by counting boxes to fit your largest value (multiples of 1, 2, 5 or 10 are best).  Plot your points.  Draw a best fit curve.  Create a title and label each axis.

49. 2.3 Recognizing relationships in data  When there is a relationship between the variables, a graph shows a clear pattern.

50. 2.3 Recognizing relationships in data  You can tell how strong the relationship is from the pattern.  If the relationship is weak, even a big change in one variable has little effect on the other.

51. 2.3 Recognizing relationships in data  When one variable increases and the other decreases, it is an inverse relationship.  Graphs of inverse relationships often slope down to the right.

52.  Nanotechnology is the technology of creating devices the size of bacteria—or smaller.  The prefix nano means extremely small.  Future applications for nanotechnology include robots that can enter your arteries and clean out blood clots, and miniature satellites that could explore the planets. NANOTECHNOLOGY