Transcript Note Card Quiz Name_____________ Date _____ Period ___ Activity 54, Analysis #3

Note Card Quiz
Name_____________ Date _____ Period ___
Activity 54, Analysis #3
Major Concepts:
► Activity
56
 There was a direct relationship between the
amount of kinetic energy put into the system
and the amount of energy transformed (thermal
energy). This was measured by an increased
temperature.
► Activity
58
 The sun is a major source of energy for
changes on earth’s surface.
 Energy can be transferred, however, it can
never be destroyed.
Major Concepts:
► Activity
73
 Making decisions often involves trade-offs----giving up one thing to gain another.
 The potential for accidents and the existence of
hazards impose the need for injury prevention
and the need to understand the physics of how
a car moves (force and motion)
What factors can contribute to a car
accident?
Speed
► Speeding
or going too fast
► In the United States, car speed is typically
measured in mph.
► km/h is used for car speed in other
countries.
► Scientists often measure everyday speeds in
m/s.
► Today, we will measure speed in cm/s.
Activity 74
Title: Measuring Speed
Background Information:
► Speed
 An object in motion takes time to change its
position. Speed is the measurement of the
rate of change in position and can be linear or
rotational. The units for speed are a distance
or an angle per unit of time, such as miles per
hour or degrees per second.
► Velocity
 Speed (s) and velocity (v) are related
concepts but are not the same thing. The
velocity of an object includes both its speed
and its direction.
Speed vs. Velocity
► What
is the difference?
The velocity of an object includes both its
speed and its direction.
More vocabulary
► tested
variable: the variable that is
manipulated (changed) in an experiment.
Also called independent variable.
► controlled
variables: the variables that
are not changed in an experiment.
► responding
variable: the variable you are
measuring in an experiment. Also called
dependent variable.
Read E-7
Part A
Problem: How can you measure the speed of
a moving cart?
Hypothesis Part A: If you ______________,
then you can ______________________.
How do people measure speed?
► Speedometer
► Radar
Gun
► Total Distance/Total Time
READ THE PROCEDURE!
Level portion of the track
Procedure
► Step
#8 – Why do you use three trials?
► Watch for ERROR. What is this?
 Timing errors may cause the time to be too long
or too short.
 You may stop the watch too soon, and sometimes
too late.
 Your reaction time may effect the timing.
 Taking the average of 3 trials can limit the error.
 You may need to do an addition trial if one is too
far off from the others.
Minimize Errors
► Release
the cart the same way each time.
► Try to get data that is ACCURATE and
REPRODUCIBLE.
► If you get 10 cm/s, 11 cm/s, and 25 cm/s,
you may want to redo the third trial.
► Put a book to stop the cart. The cart
SHOULD NOT roll off the table.
Data/Evidence:
Trial
Distance (cm)
1
100
2
100
3
100
Always include units
Time (s)
Speed (cm/s)
FIX
Average
Speed = Distance/Time
Is read “per” and means
to divide
► What
is the speed of a car that travels
 100 miles in 2 hours?
►50
MPH
► What
is the speed of a car that travels 30
kilometers in 1/2 hour?
 60 km/h
► What
Part A Discussion
is a variable?
A variable is what we change, measure and
control in an experiment. They are the
factors that influence the speed of the cart.
► What
variable did we test?
There was no tested variable. You did not
change or manipulate any factors.
► What
variables did we control?
the track (release height, angle & surface)
the cart’s mass
Part B
Problem: What will happen to the speed of
the cart if we change the release height of
the cart?
Hypothesis: If you lower the release height of
the cart, then ____________________.
How will you test your
hypothesis?
How many trials?
What are your variables other than height?
How many variables are you changing?
Calculating Speed
Why did we use the “average value”?
What does it mean if your data is accurate?
►
the ability to match the actual value
What does it mean if your data is
reproducible?
►
precision is the ability of a measurement to
be consistently reproduced
Why are these qualities important to
scientists?
Calculating Speed
Speed = distance traveled / time
What units did we use in this lab?
What units would you use to measure the speed
a car travels?
What units would you use to measure the rate at
which your hair grows?
►What
was the tested variable?
The height of the release of the cart.
This was the variable we changed or
manipulated.
►What variable was time?
►Was there a different controlled
variable in part B?
Discuss Analysis 1-3 with your group
1.
According to your data from part A, what
is the speed of the cart?
2.
According to your data from part B, what
is the effect of release height on speed?
3. List some common units for speed. Why
are there so many different units?
We choose units which are both
convenient and “friendly”
► we
use numbers between 1 and 1,000
► minutes or seconds would make some
common speeds too small (30 mph = 0.5
miles per minute
► days or years would make them too big (60
mph = 1,440 miles per day
4.
What part(s) of your experiment design in
Part B:
a. increased your confidence in your results?
b. decreased your confidence in your results?