Computer and School Network
3 Class Days
In this activity, you will study the
characteristics of the falling motion of a basketball and then
compare it to the characteristics of the motion of a projectile which
falls vertically while moving horizontally.
- Log on to the school server in the usual
- Open the Physics Explorer application (One Body model) by
double-clicking on its icon; it is found in the directory
- Choose Open... from the File menu and navigate to the Unit 3
folder in the Physics 163 folder.
- Open the file titled Exploring One Body. A multi-part Physics
Explorer simulation is opened. Open the simulation for this lab by
clicking on the "Accelerated Motion" button at the bottom of the
monitor. The Accelerated Motion Data window on the left side of
the monitor should then display the following initial values. If
not, modify them by hilighting and typing new values.
That's How the Ball Bounces:
- Run the simulation and observe the
motion of the ball. In reality, do you expect a falling
basketball to bounce back to the
initial height as it does in this simulation? ____________ Why or
why not? Explain your answer.
- Stop the simulation. The input variable
Restitution Coefficient controls the "elasticity" of the collision
between the basketball and its
surroundings (the floor). Vary its value and run until the
simulation seems more "real" to you. (Hint: Normally, a ball will
bounce each time to about two-thirds of the initial height.) What
value seems to be realistic? ____________
Velocity Change During Free-Fall:
Let us look at the motion of the ball during
- Press the "Before Hitting Ground"
- Display the velocity vector by selecting
"Velocity (V)" from the Vector Shown pop-up menu in the window on
the left side of the monitor. Run the simulation with the velocity
vector displayed. Use complete sentences to describe what happens
to the basketball's velocity as it is
- Click on the "Display Vy Graph" button. Run the
simulation and observe the slope of the vy vs. time
- How would you describe the slope of the graph? Is
it positive or negative or zero?_________ Is it constant,
decreasing or increasing? __________
- What do the above features of the graph indicate about the
acceleration of a free-falling basketball? Be extensive in you
- Calculate the acceleration of the basketball during its
- What type of force do you suppose causes this acceleration?
- What is the acceleration of the basketball at 2 seconds?
__________ Explain or PSYW.
- On the graph below, draw the velocity graph you would expect
to see as it falls, bounces, and return to its peak. For your own
benefit, make your prediction before you procede to the next step
of this activity.
- Press the "Let it Bounce" button and then click on the GO tool
to run the simulation. Check and correct your answer to the above
question (if necessary). Clearly label (or color-code) any
corrections which you make as the "Corrected Sketch." In several
sentences, describe the velocity in your own words in the space
below and explain the changes which are observed. Use the velocity
vector display to assist in your explanation. Be complete
(describing the entire down and up cycle of motion) and clear.
Combined X,Y Motion:
on the Combined X,Y Motion" button at the bottom of the monitor. A
new window titled "Combined X, Y Motion" should appear on the left
side of the monitor. See the diagram at the right.
- Click on the GO Tool and observe the
motion of the basketball.
How long did it take the
basketball to hit the ground?
basketball had no starting velocity.
If it did have an initial horizontal velocity, do you think it
will take more, less, or the same time to hit the ground?
_______________ Justify your prediction with a clearly-written
Once you have recorded your prediction
above, run the simulation with several positive and negative
values for the initial horizontal velocities between +15 m/s and
-15 m/s. (Do not clear the trace after each run.) What do you
observe? Does the horizontal velocity of the
basketball effect the time which it
takes to fall vertically? Explain.
- In the simulations, the lab was set to
leave a trace of dots as the
basketball dropped. In the space
below, use the language of physics to describe several features of
the dot patterns you observed.
- Set the Vector Display menu to "V,
by selecting this option from the Vector Display pop-up menu. Run
a simulation with vx = +10 m/s, vy = 0 m/s. Describe the behavior
of the basketball while it falls.
Comment on both the horizontal and vertical velocity
- Consider your answers to the previous
questions. How does an initial horizontal velocity affect the
vertical velocity of the dropping object?
- Do you think your answers to the
previous question would change if there were an initial negative
vertical velocity? ___________ To see, clear the trace in the
Model window (click on the "Clear Trace" butoon) and run some
set to -10 m/s using different
- What differences do you see
in the results now?
- Describe what motions stay the
- A cliff diver leaps off a high cliff
into the water below. The diver leaves the cliff with a
horizontal speed of 8 m/s. Determine the horizontal and vertical
velocities of the diver after 1 second, 2 seconds, and 3
- A blue ball rolling at a high speed
across the horizontal surface of an elevated table leaves the
table at the same time that a red ball drops off the same table
from rest. Which ball (blue, red or neither) will hit the ground
first? ________________ Justify your answer with good reasoning
and the language of physics.
- An airplane, flying at a high altitude,
drops a flare from below its cargo area. After releasing the
flare, the plane continues in its straight-line constant speed
motion as the flare falls towards the ground. Assuming that there
is a negligible amount of air resistance, five seconds later the
flare will be positioned ...
- ... directly below the
position of the cargo area.
- ... slightly behind the position of
the cargo area.
- ... slightly ahead the position of
the cargo area.
Jusify your answer with good reasoning
and the language of physics.
Use a well-written paragraph to summarize
your observations in this simulation. In your discussion, be sure to
describe the horizontal and vertical components of motion (both the
velocity and the acceleration, etc.) for a horizontally launched
projectile. Do a bang-up
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This page created by
Henderson and last updated on 8/7/97.