SPEED
Investigation 2
Part 1
Who Got There First?
Road Races
In Race 1 the pogo stick and car started
here. At the end of the race they were
here.
We were able to get the initial and final
positions for both vehicles.
We used position data and the distance
equation to calculate which vehicle went
farther.
First Arrivals
So, which vehicle arrived first in each of
these races?
On Handout #5 it shows illustrations of
two road races similar to the ones we
studied previously. In the first race the
white truck started here and the white car
started here. At the end of the race their
positions were here and here.
First Arrivals cont..
Which vehicle got to its final position first?
Which vehicle got to the 13-kilometer
mark first?
What additional information would we
need to know in order to determine which
vehicle arrived at 13 km or its final postion
first?
What is Speed
In your journal write down the word speed and
what you think that word means.
Speed is the distance an object travels in a unit
of time. The symbol for speed is lowercase v.
We use the words fast and slow to describe an
object’s speed. If an object moves a long
distance in a unit of time, we say it is going
fast. If it moves a short distance in a unit of
time , we say it is going slow.
Speed Cont.
The units of speed are distance per unit
time, such as kilometers per hour or
meters per second.
Why not miles?
What units are used in track?
A fast car might travel at 150 km/h. A
leisurely walker might travel at 1 m/s.
More Speed
An object’s speed is related to time. A
time interval is how long it takes for
something to happen. The amount of
time it takes for an object to go a certain
distance determines its speed.
Worksheets 13-15
Who Got There First?
Three races
Analog clocks
Complete the three worksheets
In your journal – write down observations
you learned or picked up on about speed.
Like…
Worksheet Observations
When two vehicles start together and go the
same distance in the same amount of time, they
arrive at the final position together.
If vehicles go different distances in the same
amount of time, the one that goes farther is
going faster.
If vehicles travel for different amounts of time,
you need to find out how far they both go in one
hour before you can compare them.
The Infinite Line
Open your books to page 1.
Answer the following questions on a piece of notebook
paper.
1. What is time?
2. What is universal time?
3. What is a time interval?
4. What are different units of time?
5. What is start time?
6. List three ancient ways of keeping time.
7. Who invented a device that measured a second?
8. Starting with seconds, list the measurements of time.
Time Travel
Part II
We just figured out how to figure out who
got there first.
Why do we need to know either how long
it took for a vehicle to travel a distance ,
or how fast the vehicle was going? Write
your answer in your journal.
Complete WS 16. WS 16 ONLY!
Worksheet Review
Be sure to write the speed as a rate
ALWAYS!!!
Speed Algorithm
Distance t Speed
100 km 2h
75 m 3 min.
60 km 4h
50 km 10 h
369 km 4.5 h
Do You Got It?
Can you write the formula or algorithm for
finding speed?
What is the symbol for speed?
What is the symbol for distance?
What is the symbol for change over time?
What’s the equation?
V = d/ t
Time Travel B
Last question – review
Complete WS 17 with your table
The initial and final positions of both vehicles are
shown on one roadway.
The vehicles travel at constant speed all the
time – no stopping or going faster and slower.
The truck is now going half as fast as it was in
the first problem.
When you get to question 2d, work with the
other in your group to figure out the equation
for calculating distance.
The Distance Algorithm
Speed t Distance
75 km/h 2h
8 m/s 10 s
5 cm/min. 60 min.
94 m/s 1.8 s
Do You Got It?
What is the equation for finding distance?
d=vx t
Definition Time
Speed (v): how fast something travels;
the distance traveled in a unit of time.
Speed Equation: v=d/ t
Distance Equation: d=vx t
Assignments
Read First in Flight and answer the
questions on pg. 6. Answer the questions
in complete sentences in your journal.
Complete WS 18 and 19.
Part 3 – Measuring Time and
Distance
What two pieces of information do you need to
know about an object in motion in order to
determine its speed?
What is the definition of speed?
What is the symbol for speed?
What units are used to describe speed?
What is the equation for calculating speed?
If you know an object is traveling at a speed of
45 kilometers per hour, how can you determine
how far it will go in 10 hours?
Determining Speed
Suppose you wanted to figure out how fast a
bicycle was going. How would you go about it?
Write the question and your answer in your
journal.
Four things you need to do:
Establish a starting position
Establish an ending position
Time how long it takes for the bike to travel the
distance
Use the speed equation to calculate the average
speed for the bike.
Focus on Time
In order to determine an object’s speed,
we need to measure the distance the
object moved, and we need to measure
how long it took to move the distance.
We know how to measure distance – we
use a meter tape.
How can measure the time it takes for the
object to move the distance?
Stop Watches
We have stopwatches for timing motion
events. They are not toys and must be
treated with care.
The watches have cords attached. The
cord is for hanging around you neck, not
for swinging it in a circle. You will lose
your opportunity to use the stopwatch if it
is not hung on your neck.
Stop Watches cont…
The stopwatches have buttons. Do not
press any of the buttons until we know
what each button does.
The button on the right turns the watch
on and resets the watch to zero after an
event has been timed. The watch turns
off automatically after a minute of
inactivity.
And more…
The middle button starts and stops the
timing function. Press once to start
timing; press a second time to stop.
Hold the watch loosely in your hand with
your thumb over the start/stop button.
Press it once and the stopwatch will start.
Press the same button a second time to
stop the watch.
Yes, there’s more…
Read the elapsed time on the screen. The
numbers represent hours, minutes, seconds, and
hundredths of a second.
Press the reset button on the right to reset the
watch to zero. It is now ready to time another
event.
Practice time
Stop at 1 s
Close your eyes and stop at 5 s
Time my hand
Playing catch
Quizzy-Poo
Complete the Response Sheet - Speed
The Dotcar
We are going to determine the speed of dotcars
rolling down slopes.
These are electronic and we only get one
chance. Each time you use these cars you will
take utmost care and have a soft catch place.
Each group is going to set up a ramp using a
board and a black thing.
The black thing should cover the bottom edge of
the slope as a transitional piece.
Dotcars
On the floor for our first time.
Your team will be assigned an elevation.
Use science books and others to meet
your elevation requirement.
Lightly tape the black thingy on the board
so it doesn’t move.
Place coats, pillows, etc. (not the big
ones) near the end of the ramp. This will
be called soft walls.
The Dotcar Experiment
Two experimental questions
How long does it take your car to travel 200
centimeters down your ramp?
What is your car’s average speed as it travels
200 cm down your ramp?
You will be assigned an elevation.
What you’re going to do…
Measure 200 cm from you xi to your xf. Mark xf
with a bit of tape.
Put up your soft wall near the end of the ramp.
Time several runs from the moment the car
begins to roll until it hits the soft wall.
Calculate the average time for a run.
Calculate the car’s average speed as it travels
200 cm.
Complete Part 1 only of WS 23.
Discussion
Discussion Questions
1. Did your car travel at the same speed
during the whole run?
2. How fast was it going at the beginning?
3. How fast was it going in the middle of
the run? At the end of the run just
before it hit the soft wall?
Average Speed
It is difficult to know how fast an object is going
at any specific time. Like our Dotcars, many
moving objects change speed all the time. Their
speed is not constant.
To get around this problem, we often use an
object’s average speed to determine how fast it
is going. If we know how far something went,
and how long it took, we can calculate the
object’s average speed.
Average Speed Cont.
Average speed is total distance divided by
the total time needed to travel the
distance.
What would be the speed of a Dotcar that
went 200 cm in 2.6s?
What is the equation then for finding the
average speed?
Write the definition and equation on your
Terms and Def. Page, and your equation
page.
Sharing Data
Part 2 of WS 23
Complete the group data table as each
table reports their findings.
Graphing
Graph distance vs. time. Time on the x-
axis and distance on the y-axis.
Label your table Mable!!!
Determine the number interval for both
variables and number the axes.
Plot the points. Write the elevation by
each data point.
Distance and time start is (0,0).
Analyzing the Data
On the back of your WS answer the following
questions.
1. Which Dotcar traveled the fastest?
2. Which Dotcar traveled the slowest?
3. What is the relationship between elevation and
speed?
4. Which Dotcar graph line has the steepest
slope?
5. Which Dotcar graph line has the flattest slope?
6. On a speed graph (distance vs. time) what
does the slope of a graph line tell you about
the speed of the object?
Using the Graph to Find Speed
Take a look at Transparency 11
These are data collected by some other students when
they did this investigation. As you can see, students
recorded the elevation, time, and distance, and they
calculated the speeds as well.
The average speed of the Dotcar on the 5-cm ramp is
48cm/s.
If we put our finger on the 1s line and move up to its
intersection with the graph line for the 5cm ramp.
From that point I can run a straight line over to the y-
axis. The place where the straight line intersects the y-
axis is the distance the car traveled in 1 s. The car
traveled 48 cm in 1 s. That gives me the speed:
48cm/s.
Find the speed of the other four cars in the same way:
Find the place where the 1-s line intersects the graph
line and run a straight line over to the y-axis
How Fast Do Things Go?
Read pgs. 7-10
Complete the worksheet.
Homework
Average Speed Practice WS 24 and 25
Next – Investigation 2 Assessment