MOTION OF A FREELY FALLING BODY Name: ____________________
Class: ____________________
Pre-Lab Questions Page
Roster Number: ____________
Instructor’s Name:___________
1. List the SI, CGS and English units for acceleration due to gravity for an
object in free fall relatively close to the Earth.
________________, ____________________, __________________
2. If a 2.50 kg physics book is dropped from rest at a height of 1.50 m, how
much time would it take the book to hit the ground? Assume no air
resistance.
3. Acceleration is a scalar quantity.
a. True
b. False
4. Velocity is a scalar quantity.
a. True
b. False
5. If a 2.50 kg physics book is dropped with an initial velocity of 10.0 m/s
from a height of 1.50 m, how much time would it take the book to hit the
ground? Assume no air resistance.
_______________________________________________________
MOTION OF A FREELY FALLING BODY
OBJECTIVE:
To measure the acceleration of a freely falling body. To verify the rate of
acceleration of a body experiencing free fall motion is not dependant on its mass.
APPARATUS:
Picket Fence (2 different
masses), PC Timer with ULI
timer
ULI
INTRODUCTION:
To find the acceleration of a
freely falling body it is
necessary to find how the
motion is changing with time.
One way to do this is to drop
BOX
an
object
through
a
photogate
and
use
a
computer timer to observe
the position, speed and
Figure 1
acceleration
along
the
vertical axis as functions of
time. Theoretically, the value
of acceleration due to gravity
of a body experiencing free fall motion is 9.80 m/s2, 980
cm/s2 and 32 ft/s2 for objects relatively close to the earth.
PROCEDURE:
1.
Make sure that the computer, ULI and photogate are connected as shown
in Figure 1. Make sure that the ULI and the computer are turned on.
2.
Click on the “Physics Lab” folder. Select the program titled “Free Falling
Body.MBL”
3.
Locate and record the mass of each picket fence provided, then align the
lightest picket fence so that its bottom is slightly above the photogate and
above the center of the opening. When released, the picket fence should
fall between the legs of the photogate and into the padded box below
without hitting any obstruction.
When ready, click on the COLLECT button and then release the picket
fence carefully.
4.
1
5.
After the picket fence passes completely through the gate, click on the
Stop button. A table and graph of your data should now appear on the
screen. If this does not happen ask the lab assistant for help.
6.
Go to the View menu and select “Auto Scale Once.”
7.
The computer can find the best straight line fit for a set of data points but it
calls it a “linear fit” line. Do this by clicking and holding on the first data
point and then drag to the last data points. Let go and the box will remain
there.
8.
Second, go up to the Analyze menu and select “Linear Fit.”
9.
Go to the View menu, select Graph options and make sure the following
are selected “Point Protector Every”, “Graph Title” and “Grid.” At the
bottom of the page in the box below “graph title” type “Velocity vs. Time”.
Click “ok”
*10.
If your data is satisfactory, save this data on your diskette and record the
name you assigned to the saved file on your data sheet. To do this select
Save As from the File menu. Save the file as a MBL file. For example,
“Light Picket Fence.mbl”
11.
Repeat the lab procedure using the heavy picket fence.
12.
After saving your data go to the main lab room and insert your computer
disk into one of the free computers.
Computer Analysis of Data:
1.
Using a free computer in SM252, click on the Physics Lab Folder
icon, then select Logger Pro icon.
2.
From the File menu select Open. Open your first saved file for this
experiment.
3.
Print the graph and data table. To do this go to the File menu and
select Printing Options and type your name and roster #. Under the
comment section type either “Light Picket Fence” or “Heavy Picket
Fence”, whichever pertains to your graph. Select the date option and
then select Page Setup. Click on “Landscape” and hit the “ok” button
two times. Go to the File menu and select “Print screen” and hit “ok”.
4.
Repeat for the second graph.
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PRACTICE QUESTIONS:
1. How does your value from the graph of the acceleration due to gravity
compare to the accepted value? Calculate the %error of your experiment
to determine the answer to this question.
2. Was your experimental value too high or too low?
3. How did the mass of the picket fence affect its acceleration?
4. How would starting the picket fence with an initial velocity other than zero
affect your experimental value of acceleration due to gravity?
5. What affect would wind resistance have on your experimental value of
acceleration?
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