Transcript Foundations of Physical Science

Foundations of Physical Science
Unit One: Forces and Motion
Chapter 1: Science and Measurement
• 1.1 Time and Distance
• 1.2 Investigations and Experiments
• 1.3 Speed
Learning Goals
• Accurately measure time using electronic timers and
photogates.
• Use decimals to represent fractions of a second.
• Develop a research question or hypothesis that can be
tested.
• Identify the variables that affect motion.
• Develop an experimental technique that achieves
consistent results.
Learning Goals (continued)
• Draw conclusions from experimental results.
• Accurately measure distance.
• Identify metric and English units of distance.
• Convert between units of distance.
• Calculate speed in units of inches per second, feet
per second, and centimeters per second.
Vocabulary
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cause and effect
controlled experiment
controlled variables
distance
English system
experiment
experimental technique
experimental variable
hypothesis
investigation
length
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measurement
metric system
procedure
research question
scientific evidence
scientific method
second
time
trial
variables
1.1 Time and Distance
Two Ways to Think about Time
• What time is it?
• How much time?
How is Time Measured?
• Time comes in mixed units.
– Seconds are very short.
– Hours and minutes are more convenient for
everyday time measurement.
Electronic Timers
• Have displays that
show mixed units.
• To read a timer you
need to recognize and
separate out the
different units.
• Colons (:) separate
the units.
Measuring Distance
• Describes how far it is from one point to
another
• Measured in units of length
• Two common systems of units:
– English (inches, feet, miles)
– Metric (millimeters, centimeters, meters,
kilometers)
Measurement and the English System
Measurement and the Metric System
Measurement
• Units were invented so people could
communicate amounts to each other.
1.2 Investigations and
Experiments
Designing Experiments
• How do we ask questions and get answers
from nature?
Experiment
• Any situation we set up to observe what happens.
• In science, we usually plan our experiments to give us
measurements, which are observations we can record
and think about.
• Experiments have questions associated with them.
• Experiments are the way we ask questions of nature.
Scientific Method
• Developed by Galileo and the English
philosopher Francis Bacon in the 16th century
• Based on rational thinking and
experimentation
Designing Experiments
• Start with a good question
• Identify all the factors when designing
experiments
• Variables
• Change 1 thing at a time
• Control variables and experimental variables
Hypothesis
• An educated guess about what will happen
Experimental Techniques
• Experiments often have several trials
• Experimental technique
• Procedures
• Scientific results must always be repeatable
Limitations
• Science deals only with hypotheses that are testable
• Science is restricted to the observable natural world
– Supernatural “above nature” cannot be explained
– Philosophical questions cannot be answered
Pseudoscience
• Some belief systems are not science but
pretend to be
• Phrenology: the study of the surface bumps on
a person’s head to identify health and
personality
Pseudoscience
• Astrology: the study of the stars and
planets and their movements as well as
their affects on the lives and behavior of
human beings
The Search For Order
• Science
• Art
• Religion
Technology
• Practical use of the findings of science
• Science: concerned with gathering knowledge and
organizing it
• Technology: lets humans use that knowledge for
practical purposes, and it provides the instruments
scientists need to conduct their investigations
Technology
• Can be helpful and can be harmful
• Example: find fossil fuels used in countless
ways while damaging the environment
• Technology is our tool to fix these problems
The Sciences
• Life Sciences: biology, zoology, botany, etc.
• Physical Sciences: physics, chemistry, gemology,
meteorology, astronomy
1.3 Speed
What is Speed and
How is it Measured?
What Do We Mean By Speed?
• The speed of an object is a measure of how quickly the object
gets from one place to another.
• To determine a speed, you need to know two things:
– the distance traveled.
– the time taken.
Speed
speed (m/sec)
v=d
t
distance traveled (m)
time taken (sec)
What’s the “v” for?
• Speed: the distance covered per unit of time
• Velocity: speed and the direction of an object
• Speed: 60 km/h
• Velocity: 60 km/h due East
• Vector Quantity: a quantity that specifies both
magnitude and direction (example: velocity)
Concepts of Speed and Velocity
• Constant speed:
steady speed;
doesn’t speed up
or slow down
• Constant velocity:
both constant
speed and
constant direction
How to Solve Scientific Problems
• Step 1
– Identify what you are asked.
• Step 2
– Write down what you are given.
• Step 3
– Write down any relationships you know that involve any of the
information you are asked, or given.
• Step 4
– Pick which relationship to start with and try to arrange it to get the
variable you want on the left-hand side of an equal sign.
• Step 5
– Plug in the numbers and get the answer
Example
• What is the average speed of a cheetah that sprints
100m in 4s? How about if it sprints 50m in 2s?
• In both cases the answer is 25 m/s
Average speed = distance covered = 100m = 50m = 25m/s
time interval
4s
2s