Download Module 3 – Free Falling Bodies

Module 3 – Free Falling Bodies
INTRODUCTION
In the motion experiment1 , we studied uniform motion and uniformly accelerated motion. In
this experiment, we will observe free falling bodies, which are examples of uniformly accelerated
motion.
Recall that uniformly accelerated motion is motion in one direction accelerated by a constant
force. Free falling bodies fit this definition since we define a freely falling body as a body being
accelerated exclusively by the force of gravity. No other forces are considered; so the effects of
wind, air resistance, and the rotation of the Earth are not included in the analysis.
Figure 1
APPLICATION OF NEWTON’S SECOND LAW
An interesting attribute of freely falling objects is that all objects fall at the same rate. This
means that two objects dropped together from the same height will hit the ground at the same
time. As stated in the previous section, free falling objects are accelerated by the force of gravity.
On Earth, the acceleration due to gravity is approximately 9.8 m/s2 . Physicists use the letter g to
represent the acceleration due to gravity.
Newton’s Second Law in equation form is F = ma, but since free falling objects are accelerated
by gravity, Newton’s Second Law becomes F = mg.
Suppose we drop two balls, one with a mass of 1 kg and the second with a mass of 2 kg. If we
apply Newton’s law to these two masses, we can calculate the force of gravity on each object.
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../lab 2 1 intro/manual.html
c
2012-2013
Advanced Instructional Systems, Inc. and Embry-Riddle Aeronautical University
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Figure 2
Force on the more massive ball = (2 kg)(9.8 m/s2 ) = 19.6 N
Force on the less massive ball = (1 kg)(9.8 m/s2 ) = 9.8 N
WAIT A MINUTE! I thought that the two objects hit the ground at the same time. How can
this be when the force on the more massive ball is twice that on the less massive ball?
This is an interesting finding. What Newton’s Second Law tells us is that in order to accelerate
the 2 kg mass by the same amount as the 1 kg mass, the FORCE has to be TWICE the size.
TO SUMMARIZE:
All objects fall at the same rate.
The force on free falling objects depends on their mass.
PROCEDURE
You will observe the experiment performed and fill in your data sheets.
1
Open the experiment instructions and worksheet.
c
2012-2013
Advanced Instructional Systems, Inc. and Embry-Riddle Aeronautical University
2
•
Free Falling Bodies Experiment Instructions (HTML2 or PDF3 )
•
Free Falling Bodies Experiment Worksheet4
2
After you have opened the instructions and worksheet, select and watch the Experiment Video
(the Experiment Video is available in your course LMS).
3
Record your data in the worksheet. (You will need it for the lab report assignment in
WebAssign.)
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../lab 3 1 procedure/manual.html
../lab 3 1 procedure/manual.pdf
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../lab 3 1 procedure/worksheet.pdf
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c
2012-2013
Advanced Instructional Systems, Inc. and Embry-Riddle Aeronautical University
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