PPT
Dropping Things
Developer Notes
 What should the order be? In the scope & sequence, “Electric Cars” is first, then “Dropping
things.” However, in class, we did “Dropping Things” first, then “Electric Cars.” I prefer
“Electric Cars” first, then “Dropping Things” (this is also how we presented it in the summer
wrkshp). (sc)
 There is this very nice discussion about replication and lurking variables, but I’m not sure if
it fits in this activity. Perhaps move it to “Dollar Drop” ????? I labeled it as an extension.
Version Date
Who Revisions
05
8/07/03 sc
 Added warm-up question
 Revised Presentation section to describe set-up and materials
for each station
 Eliminated references to graph from “Dollar Drop”
 Eliminated direction to make predictions at each station- as
this takes too long
 Eliminated ping-pong ball- as dropping two different types of
balls was confusing
Goals
 Have students qualitatively describe what happens as an object falls
 Students should understand qualitative & quantitative data
Concepts & Skills Introduced
Area
Science
Physics
Concept
Qualitative vs. quantitative data
Acceleration
Time Required
About 1 class period
Warm-up Questions
Set up different masses (or any other objects) on a balance and have the students describe them
qualitatively and quantitatively. (This is a nice question to use the day after this lesson as a
review).
Presentation
The series of stations is intended to have students observe the motion of falling objects. They
should observe that things dropped from higher heights end up “falling faster.” Balls bounce
higher, ink splatters more, etc. This hints at acceleration (changing speed) and that falling
objects (like our rulers) accelerate.
This is also a good place to introduce the differences between qualitative and quantitative data.
Both types of data are useful for scientists; this activity emphasizes making qualitative
observations about the falling objects.
106752556
eb
Page 1 of 6
PPT
Dropping Things
Divide the class into groups (groups of 3 or 4 work nicely) and have the groups rotate through
the stations.
Below is a description of the materials and set-up for each station:
Station 1: Clay Ball
 Materials
1 or 2 soft clay balls
Fresh Play-Doh may also be used (older Play-Doh tends to be too elastic and will bounce)

Set-Up/ Procedure
Students should drop the clay ball from various heights and notice that balls dropped from
higher up have a bigger “splat.” The flat part from where it lands on the floor is bigger.
Station 2: Plastic wrap and ball bearing
 Materials
Paper or plastic cup
Plastic wrap (several pieces)
Rubber band
Ball bearing

Set-Up/ Procedure
Students should drop the ball bearing from various heights and notice that from higher up the
ball bearing can tear through the plastic wrap.
Station 3: Ink drops
 Materials
Ink (watered down) or food coloring
Medicine dropper or plastic pipette
Large sheets of paper

Set-Up/ Procedure
Students should carefully squeeze drops of ink from various heights and notice that from
higher up the ink splatters more.
Station 4: Ball bounce
 Materials
1 or 2 tennis balls

Set-Up/ Procedure
Students should drop the tennis ball from various heights and notice that from higher up the
ball bounces higher.
Station 5: Screwdriver and Play-Doh
 Materials
Screwdriver
106752556
eb
Page 2 of 6
PPT
Dropping Things
Play-Doh in container
Long plastic tube (fairly flexible)

Set-Up/ Procedure
The plastic tube is to guide the screwdriver straight into the Play-Doh. Students should place
the screwdriver in the tube and squeeze the tube to hold the screwdriver point down.
Students should release the screwdriver from various heights and note how deep the
screwdriver goes into the Play-Doh.
Station 6: Ball bearing on a ramp
 Materials
Ball bearing
Ruler ramp or Galileo ramp

Set-Up/ Procedure
Set up the ramp at the edge of table so the ball will roll off and onto the floor. Students
should release the ball from different heights on the ramp and notice where it hits the floor.
Station 7: Washers on a string
This station is tricky. You need to drop the string from fairly high up (like the ceiling) and the
string tends to get tangled (damn entropy). So, you may want to do this just as a teacher demo.

Materials
String (about 5-6 m long)
8 washers (or bolts)
Empty metal trashcan (or something to enhance the sound)

Set-Up
Starting at one end of the string, tie one washer to the string every 40 cm. Leave the rest of
the string free. (A handy way to store your string is to wrap it around a piece of cardboard).

Procedure
Hold the string so that the bottom washer rests on the bottom of the metal can and the rest of
the string is vertical. You may have to stand on a chair or table. Alternatively, you can use a
long stick with a nail protruding horizontally at one end. Loop the long part of the string
over the nail and hold up the stick so that the string is vertical. Let go of the string and let it
slide over the nail. The students should hear that the time intervals between washers hitting
the can get shorter.
106752556
eb
Page 3 of 6
PPT
Dropping Things
Background
When we recorded the distance that our ruler dropped before we caught it, we were able to
record a number. That is, we had some quantitative data or something to which we could put a
quantity. Today, we’ll be mostly observing and describing what happens when we try some
different procedures without recording any numerical values. We’ll be recording qualitative data.
Both are important in science, but we use them in different ways. As you work through the
stations ask yourself which data are qualitative and which are quantitative. Are any of them
both? Could you make them more quantitative? How? Think about how each type of data is
valuable to our research on falling objects.
Problem
Describe the motion of falling objects.
Materials
Vary with stations
Procedure
Follow the directions for each of the stations. When you are done leave your station neat and set
up for the next group.
For each station:
 Write the name of the station.
 Identify the independent and dependent variables.
 Record your observations of what happens. Record qualitative data (and quantitative if you
want to). Meter sticks are provided to assist you.
Station 1: Clay ball
Drop the clay ball onto the floor from various heights. Before each drop, roll the ball back into a
round shape.
Station 2: Plastic wrap and ball bearing
Stretch plastic wrap over the plastic cup, holding it on with the rubber band. Drop the ball
bearing onto the plastic wrap from gradually increasing heights.
Station 3: Ink drops
Use the dropper to squeeze drops of ink onto the paper from various heights, beginning at about
1 cm.
Station 4: Ball bounce
Drop the tennis ball from various heights.
Station 5: Screwdriver and Play-Doh
To drop the screwdriver, put it in the tube, squeeze the tube to hold the screwdriver point down,
and place the end of the tube on top of the Play-Doh. Then release the screwdriver. Note how
deep the screwdriver goes into the Play-Doh. Smooth the Play-Doh out before each drop. Drop
106752556
eb
Page 4 of 6
PPT
Dropping Things
the screwdriver from various heights.
Station 6: Ball bearing on a ramp
Roll the ball bearing off the ramp from various heights. Note where the ball hits the floor.
Station 7: Washers on string
There is a long string with washers at regular intervals. Loop the long part of the string over the
nail on the stick. Hold the stick up so that the bottom washer rests on the bottom of the metal can
and the rest of the string is vertical. Release the string. What do you hear? Please try to keep the
string from getting tangled. Call the teacher if you have trouble with tangled string.
(Your teacher may do this as a demo).
Summary
1. What happened when you dropped things from higher up?
2. Do you think that there is some additional factor about falling objects that may be
involved with our ruler drop experiment?
Extension
Consistency and Control are important features of any scientific investigation. Ideally, you
should be testing the effect of only one variable at a time, and doing it the same way every time.
Otherwise, how do you know which variable is influencing the results that you are getting?
There is a common occurrence in science called the lurking variable. The following scenario is
commonly used as an example of the lurking variable. There is a correlation between the amount
of ice cream sold and the number of murders committed in Chicago (this is a real statistic). So,
ice cream is causing people to be murdered. Do you really think that is true? There is actually a
third variable, a lurking variable, in this scenario. How hot it is influences both the amount of ice
cream sold, and the number of murders. Heat is our lurking variable. It is important that we try to
control everything that we can about our experiments so that we are not deceived by any lurking
variables.
What kinds of things did you do to control your tests during the ruler drop experiment?
Could there be a lurking variable in our ruler drop experiment that influenced our data?
Replication is what we do to make sure that we aren’t thrown off by a fluke result. Think
of it as getting a second opinion from your doctor. Suppose the first time you make your test a
sudden gust of wind enters the room. The result you get may not accurately reflect what is really
going on, and if you use only that result to explain what you saw, it may not be an accurate
representation. To avoid this, we repeat our experiments over and over, to make sure that your
results are consistent and what we can probably expect to happen every time we repeat the
experiment under the same conditions. You should always write up your procedure clearly so
that someone else could repeat your experiment if they wanted to.
Can you think of any times were you might not repeat an experiment?
106752556
eb
Page 5 of 6
PPT
Dropping Things
Look back over your ruler drop data, and compare your first result to the averages you got. Share
your information with the class. Did anyone get a first result that was very different from the
average and would have caused them to misinterpret their results?
106752556
eb
Page 6 of 6