Free F
A
L
L
Part 1
1. Listen to the recorded sounds made as two strings were
dropped into a wastebasket.
2. What do you notice about the sounds of “sound #1” and
“sound #2”. Record your observations in your notebook.
3. A and “B are representations of washers on strings. What
did you notice about each string? Record your observations in your
notebook.
4. During recording, the sound levels are displayed on a screen.
We captured an image of that screen. Examine the image.
Based on your observations, which string do you think made which noise?
Draw arrows to indicate your ideas.
A
Sound #1
Sound
#2
Why? Justify your answer.
In small groups, discuss your observations about the sound,
the strings and the association you made above.
B
Free Fall Part 2
When a falling object is free of all restraints – no friction, air, or otherwise,
and falls under the influence of gravity alone – the object is in free-fall.
Free-fall from Rest
Time of
Instantaneous
Fall (sec) speed (m/s)
0
0
1
10
2
20
3
30
4
40
5
50
6
60
1. Examine the data in the table which shows the instantaneous speed of an
object, let’s say a rock, in free-fall at 1-second intervals. What patterns do
you notice?
2. What is the acceleration of the rock in free-fall whose data is represented
above? Be sure to include units. Explain where this value and its
appropriate units came from.
3. For freely falling objects it is customary
to use the letter g to represent acceleration (because the acceleration is due
to gravity). What is the value of g?
4. Imagine a speedometer is attached to
our freely falling rock that tumbles off a
cliff (a really high cliff) from rest. What
would be the speedometer’s reading on
the falling rock
a. 3.5 sec after it begins its cliff
tumble?
b. 6 sec after it begins its cliff
tumble?
c. 100 sec (remember, the cliff is
REALLY high) after it begins its
cliff tumble?
5. What equation did you use (or could you
have used or could you use in the
future) to answer (4) a-c (or questions
like a-c)?
6. Graph the data in the data table.
7. Answers to which scenario(s) 4 a-c can be determined using the graph?
8. Answers to which scenario(s) 4 a-c are predictions based on the data?
9. In addition to the data table, list 2 other ways we have represented the
data in this scenario about the rock tumbling off the cliff. Which of these 3
is the actual data?
10. Using the data and all of its representations, make a summary statement
about the relationship between the speed of an object under free fall and
time.
11. What representation(s) of the data did you find most useful when making
your above summary statement? Explain.
Free Fall Challenge #1
The rock in the above scenario tumbled off the cliff. What would happen to its
speed if it had been thrown downward? Write an equation to represent this
relationship.
Free Fall Part 3
So far we have been thinking about objects moving straight downward in the
direction of gravity. How about an object thrown straight upward?
Think about the rock again (or another similar rock). This time there is a thrower
on the edge of the cliff (or another similar cliff) who throws the rock up with a
speed of 30 m/s. It is reasonable for the rock to reach its peak ~3 sec after it has
left the thrower’s hand, at which time it will change its direction of motion from
upward to downward.
On the way down, the rock avoids the cliff and continues to fall. (Focus on the
rock once it is released from the thrower’s hand).
12. Draw a picture of the above scenario.
• Show the rock’s path and its location at 1-second intervals.
• Calculate the rock’s instantaneous speed (think speedometer here!) at
each 1-second interval and include it on your picture
• Include at least 4 seconds of time after the rock changes its direction of
motion from upward to downward.
• Represent your group’s thinking on a white board and as a group
develop a plan to share it with the class.
13. What patterns do you notice?
14. Which part of your picture is most like the first scenario when the rock
simply tumbled off the cliff? Explain.
15. What is the instantaneous speed of the rock at the peak of its path at the
instant when the direction of its motion is just changing from upward to
downward?
16. How long will it take before the rock passes the person on the edge of the
cliff?
Free Fall Challenge #2
A ball is thrown straight upward and leaves your hand at 20 m/s. What
predictions can you make about the ball and its motion?
Free Fall Wrap Up
Think back to the strings. Draw arrows to indicate which string made which
noise.
Sound #1
Sound
#2
Why? Justify your answer.