Free Fall Simulation - Falling From Rest
In this activity, you will use the Interactive
PhysicsTM program to simulate the motion of a ball
falling freely from rest. When you first load the simulation file, it
is set up to simulate free fall near the surface of the Earth, where
g = 10 m/s2 (approximately). After investigating this
motion, you will alter the value of g to simulate free fall on the
Moon, where g = 1.63 m/s2.
The Interactive PhysicsTM Free Fall
- Double-click on the file "ip_frefall_sim" which you will find
in the "Group Shared" folder. This will start the Interactive
PhysicsTM software and load the free fall simulation as
shown in the diagram at right. (Interactive PhysicsTM
software may not be available on all computers.)
- When you click "Run" on the toolbar, the ball will begin to
fall. Notice how the position, velocity, and acceleration meters
change as the ball moves. To stop the simulation, click "Stop"
(the "Run" button changes to a stop sign while the simulation is
running.). Note that you can start and stop the simulation by
alternately clicking "Run" and "Stop". To reset the simulation,
click the "Reset" button.
- Construct a data table in
which you can record the position, velocity, and acceleration for
the ball for each half second from 0 seconds to 4 seconds.
- Reset the simulation and click "Run". When the timer is near
0.5 seconds, click "Stop". Use the frame advance buttons to move
the timer to precisely 0.5 second, and enter the data for
position, velocity, and acceleration in your data table. Click
"Run" again, and stop the simulation and record your data for 1,
1.5, 2, 2.5, 3, 3.5, and 4 seconds.
- Pull down the World Menu, and select
"Gravity...". Use the slider to change the free fall acceleration
to approximate gravity on the moon (about 1.630
The Gravity Dialog
- Construct a second data table (be sure to label which data
table is which!) in which you can enter the position, velocity,
and acceleration of the ball on the moon each half second from 0
to 4 seconds.
- Run the simulation and record your data for the moon.
- Construct position vs. time, velocity vs. time, and
acceleration vs. time graphs for the motions. You can put the
graphs for both the Earth and the Moon on the same set of
- As the ball falls, what happens to its velocity? (Remember
that a quantitative description is superior to a
- As the ball falls, what happens to its acceleration?
- How does free fall on the Moon compare to free fall on Earth?
(How is it the same, and how is it different?)
- For free fall on Earth (g = 10 m/s2), calculate the
velocity and distance fallen for a ball starting from rest which
falls for 4 seconds. Show a neat and organized calculation.
Compare your results with the simulation results.
- For free fall on the Moon (g = 1.63 m/s2),
calculate the velocity and distance fallen for a ball starting
from rest which falls for 4 seconds. Show a neat and organized
calculation. Compare your results with the simulation
last update October 18, 2002 by JL