Unit 1, Chapter 3

CPO ScienceFoundations of Physics

Chapter 9Chapter 9

Unit 1: Measurement and Motion

3.1 Speed

3.2 Observations of Motion

3.3 Analyzing Motion with Graphs

Chapter 3: Models of Motion

Chapter 3 Objectives1. Calculate time, distance or speed when given

two of three values.2. Identify the variables in an experiment.3. Design an experiment where all the variables

but one are controlled.4. Draw and interpret graphs of experimental data

including speed versus position, speed vs. time, and position vs. time.

5. Use a graphical model to make predictions that can be tested by experimenting.

6. Determine speed from the slope of a position versus time graph.

7. Determine distance from the area under a speed versus time graph.

Chapter 3 Vocabulary Terms

speed distance time variables model initial

speed angle friction

experimental variable

control variables trial experimental

technique procedure dependent variable y-axis x-axis independent

variable

graphical model graph position origin rate slope average speed instantaneous

speed

3.1 SpeedKey Question:

What is speed and

how is it measured?

*Students read Section 3.1

AFTER Investigation 3.1

3.1 Speed

v = d t

Distance traveled (m)

Time taken (sec)

Speed (m/sec)

3.1 Calculate speed

A bird is observed to fly 50 meters in 7.5 seconds.

Calculate the speed of the bird in m/sec.

3.1 Calculate distance

How far do you go if you drive for 2 hours at a speed of 100 kilometers per hour?

3.1 Calculate time and distance A space shuttle is traveling at

a speed of 7,700 m/sec. How far does the shuttle

travel in kilometers in one hour?

At an altitude of 300 kilometers, the circumference of the shuttle’s orbit is 42 million meters.

How long does it take the shuttle to go around the Earth one time?

3.1 Units for Speed

3.1 Calculating Speed

Why the letter v is used for speed...— We use the letter v to represent speed in a

formula. — If this seems confusing, remember that v

stands for velocity.Speed is a single measurement that tells how fast you are going, like 100 km/h.

Velocity means you know both your speed and your direction.

3.2 Observations of MotionKey Question:

Can you predict the speed of a ball rolling down a ramp?

*Students read Section 3.2 AFTER Investigation 3.2

3.2 Observations of Motion Variables that can affect the speed of a marble.

3.2 Observations of Motion Experimental Techniques

— Control and experimental variables are important in controlled experiments.

3.2 Observations of Motion Experimental Techniques

— Experimental technique is how you actually do the experiment.

— Each time you run the experiment is called a trial.

Data for three trials

3.2 Observations of Motion Scientific results

must always be repeatable.— A procedure is a

collection of all the techniques used to do an experiment.

— Writing good procedures is the best way to ensure that others can repeat and verify your experiments.

A sample procedure

3.2 Graphical Data To a scientist, a

graph is a language that shows the relationship between two variables.

By convention, graphs are drawn a certain way just like words are spelled certain ways.

This graph shows the relationship between speed and distance.

3.2 Graphical Data Speed, the

dependent variable goes on the y-axis.

Distance is the independent variable and goes on the horizontal or x-axis.

This graph shows the relationship between speed and distance.

3.2 Using graphical models

If the graph is created from accurate data, the prediction will also be accurate.

3.2 Recognizing relationships in data Cause and effect

Patterns indicate relationships

Strong relationship between variables

NO relationship between variables

3.2 Recognizing Relationships in Data

3.3 Analyzing Motion with GraphsKey Question:

How do you model motion?

*Students read Section 3.3 AFTER Investigation 3.3

How to make a graph

1. Decide what to put on the x and y axes.

2. Make a scale by counting boxes to fit your largest value (multiples of 1, 2, 5 or 10 are best).

3. Plot your points.4. Draw a best fit curve.5. Create a title and label

each axis.

Speed vs. Distance

3.3 Position time graph

3.3 Interpret a position time graph The position versus time

graph shows a boat traveling through a long canal.

The boat has to stop at locks for changes in water level.— a) How many stops does

the boat make?— b) What is the boat’s

average speed for the whole trip?

— c) What is the highest speed the boat reaches?

3.3 Slope The slope of a line is the ratio of the “rise” (vertical

change) to the “run”(horizontal change) of the line.

3.3 Constant Speed

On this graph, a constant speed is a straight horizontal line.

Application: Slow-motion Photography