Experiment 3.2
PROJECTILE MOTION
Honors Physics Lab:
Purpose
The purpose of this lab is to study the horizontal and vertical components of projectile motion.
Theory
If there were no gravity, a thrown ball would continue in a straight line forever always moving at the same velocity. The distance it would travel could be
expressed with the following formula:
x = vt
Where: v is the velocity in the horizontal direction
In the case where a ball is dropped from rest in the presence of gravity, the
distance the ball falls is given by the following equation:
x =
1
2
at
2
Where: a is the acceleration of gravity
When a ball is thrown sideways, a combination of both of these straight-line
motions occur -- one horizontal and one vertical. Both of these motion are
independent of each other and only the vertical undergoes acceleration. Thus
the x and y position of a projectile can be given by the following parametric
equations:
x - position = vH t
y - position = vV t +
1
2
at 2
Where v H is the original horizontal velocity
Where vV is the original horizontal velocity
Where a is the acceleration of gravity
- 9.8
m
s2
Procedure
1. Assemble a ramp on the top of your lab table similar to the one
shown on the right. The ball must leave the edge of the lab table
horizontally -- so leave a minimum of 25 centimeters between the
end of your ramp and the edge of the table. (A --> B)
2. Place tape between the ramp and the table top so that the ball has
a smooth path between the two surfaces. If the ball bounces when
reaching the table top, it may miss one or both of the photogates.
3. Place a photogate at both point A and B. Record the distance
between them. You will use the computer to measure the time interval the ball requires to travel from
point A to point B. Its velocity can be calculated by dividing the distance between the photogates by
the time required.
4. Place a small piece of tape at an arbitrary point on the ramp. This will be your starting position for the
ball for your trial.
5. Start the "Precision Timer" program. Choose “6500 Interface”, "Pulse Timing", "Pulse 1-2", and
"Normal Time Display". Allow the ball to roll down the ramp from your marked starting position a
minimum of five times. DO NOT allow the ball to contact the floor during these timings! Once you
have five good times, press <ENTER> and then choose "Display Data Table". Record the mean time
in your data table.
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Experiment 3.2
6. Measure the vertical distance from the end of the ramp to the floor. Record this in your data table.
Calculate the amount of time required for an object to free-fall from rest through this distance. This is
the amount of time that the ball will be in flight. You may wish to consider the height of the container in
your calculations.
7. From the time of flight, calculate the horizontal distance that the ball should travel before hitting the
floor. Mark this position and then call your instructor over so that the metal container can be placed at
the calculated location.
8. Roll the ball down the ramp from the marked position and determine where it impacts on the floor
(hopefully in the container).
9. Repeat steps 4 - 8 a minimum of four times. You should use a different starting position for each trial.
Data Table
Trial
Number:
1
Distance
A --> B:
Ave Time
A --> B:
Velocity
A --> B:
Vertical
Height:
Time of
Flight:
Calculated
Distance:
Actual
Distance:
Hit Can
Signature:
2
3
4
5
Analysis/Questions
1. What aspect(s) of your ramp determined the ball’s initial launch velocity?
2. What factors may have made the ball miss the target container?
3. You probably noticed that the horizontal distance (range) that the ball traveled was directly proportional
to the velocity at which the ball left the ramp. What effect do you think air resistance had on this lab?
4. Make a graph of velocity versus range for this experiment. How are the two quantities related?
5. Graph the path of one of your trials using the formula:
y
xsin 
4.9x 2
 2
2
cos  vo cos 
by placing your values for the launch angle and initial velocity into the equation.
You can use Derive! or Excel to graph your formula. Start Derive by double-clicking on the Derive
icon in the “Physics Lab” program group. Once the program is running, choose:
(A)uthor
and then enter your equation and press <ENTER>
(P)lot
(P)lot
<SHIFT> + <PRTSCR> to send the graph to the printer
[HKIS -- 40628627 Lab]
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Last Updated: 6/20/2022 6:57:00 PM