an introduction to physics chapter 1-1. what is physics? physics is the study of matter, energy and...
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An Introduction to PhysicsAn Introduction to Physics
Chapter 1-1
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What is Physics?What is Physics?
• Physics is the study of matter, energy and their motion, as well as space and time.
• Physics is an experimental science.• Scientists make observations• Develop testable theories• Test theories against new observations
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In the beginning…In the beginning…
• Physics is the oldest of all academic disciplines.
• Astronomers were the first physicists.• Early Astronomers were not experimental
scientists. • Would think about there observations and
develop reasonable explanations that fit the data.
• Not very good at predicting the outcome of events.
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Areas of PhysicsAreas of Physics
• Mechanics- Motion and its causes• Thermodynamics- Heat and Temperature• Vibrations- Repetitive Motion• Optics- Light• Electromagnetism- Electricity, Magnetism, and
Light• Relativity- Particles moving at high speeds• Quantum Mechanics- Behavior of tiny particles
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The Scientific MethodThe Scientific Method
1. Make observations and collect data that leads to a question (How/Why?)
2. Formulate testable explanation(s) to fit that data.3. Design and perform experiment to test
explanation(s)4. Interpret results of experiment and revise
explanation(s) if necessary.5. State conclusion in a way that can be evaluated
by others.
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ModelsModels
• The subject matter covered by physics is very complex.
• Physicists often use simple models to explain the most fundamental aspects of a situation.
• We often neglect variables that affect the situation only slightly but make calculations very difficult.
• In spite of these simplifications we can still make rather accurate predictions about various situations.
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Models (cont)Models (cont)
• Models help develop explanations.• Galileo performed a ‘thought experiment’
that enabled him to disprove the notion that heavier object fall faster than lighter ones.
• He imagined two equal bricks falling together. They must fall at the same rate.
• He then imagined the same two bricks falling but they were tied together, would they fall any faster?
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Models and ExperimentsModels and Experiments
• Galileo had no way of measuring the speed of falling objects.
• He used a model of a ball rolling down a ramp to model the act of falling, the steeper the ramp the closer the model represented the actual situation.
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Measurements in Experiments
Measurements in Experiments
Chapter 1-2
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Numbers as MeasurementsNumbers as Measurements
• Measurements in Physics require more than just numbers.
• Each measurement will be associated with a quantity as well as what kind of quantity is being measured, referred to as a dimension.
• There are 3 dimensions we talk a lot about in physics• Distance
• Mass
• Time
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Standards of MeasurementStandards of Measurement
• So everyone can understand values that are reported from an experiment, all scientists must use the same standard of measure.
• SI is the standard for science.• Distance: Meter = Distance traveled by light in
a vacuum in 3.3 x 10-9seconds.• Mass: Kilogram = Mass of 1 Liter of Water• Time: Second = 9,192,631,700 times the period
of radio wave emitted from a cesium-133 atom.
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A Wide RangeA Wide Range
• Physicists deal with the wide range of numbers using two methods
• Prefixes are used to change the units.• Ex. 1 meter = 1000 millimeters
• Scientific notation also helps to make small or large numbers more manageable.
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Scientific NotationScientific Notation
• To convert a number into scientific notation. • Move the decimal place so there is only 1 digit to
the left of the decimal. • Count the number of places the decimal moved. • That number becomes the exponent on the 10. IF
the number is less than one the exponent will be negative. (if the decimal moves to the left)
• To enter into a calculator use the EE button.
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Accuracy vs PrecisionAccuracy vs Precision
• Accuracy is how closely a measurement agrees with the true value.
• Precision is how exact or refined the measurement is. (How repeatable is the measure?)
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Problems with AccuracyProblems with Accuracy
• Problems with accuracy are usually due to error.
• It can be caused by having un-calibrated or poorly calibrated measuring devices.
• Also human error can lead to inaccurate measurements.
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Problems with PrecisionProblems with Precision
• Problems in precision generally are a result of the limitations of the measuring device.
• When measuring in science we always estimate the next decimal place
• Imprecise measurements are dealt with in science using Significant Figures
• If a mountain’s height is known to the nearest 5m then would adding a 1 meter pile of rocks at the top change its height?
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Significant Figures (SigFigs)Significant Figures (SigFigs)
• When doing calculations in physics we will always report the answer to have the same number of sigfigs as the value in our calculations with the least number of sigfigs.
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What are SigFigs?What are SigFigs?
• All non-zero numbers.• Some zeros are also sigfigs.
• Zeros between nonzero digits are significant• Zeros to the left of nonzero numbers are not significant• Zeros at the end of a number and to the right of a
decimal are significant• Zeros at the end of a number and to the left of the
decimal are only significant if you have made the measurement.
• http://science.widener.edu/svb/tutorial/sigfigures.html
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Dimensional AnalysisDimensional Analysis
• Most of the problems you will face in physics ask you to take information you have and ask you for information you don’t have, usually of another unit or dimension.
• Conversion factors can be used to get this information as long as you properly align the factors so the units cancel (or divide out)
• Dimensional Analysis uses a series of fractions to convert your given information to the information that was requested
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How many seconds are in a Day?How many seconds are in a Day?
• While you may not have this figure memorized, you can use information you do have to find out.
• Step 1. Determine the units of the answer.• if you want to know how many seconds are in a day
you want sec/day.
• Step 2. Determine factors that you already know, or are given by the problem.• You know that there are 24 hrs/day, 60min/hour, 60
sec/minute.
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Sec/Day (cont)Sec/Day (cont)
• Step 3. If you align these figures properly the units will cancel and you will be left with sec/day.
• Keep in mind that all of the fractions we just listed can be inverted (1day/24hours)
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