Lab 4 - Projectile Motion
EQUIPMENT NEEDED
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two photogate and bracket
projectile launcher
ball, plastic, 1 inch diameter
time-of-flight timing pad
extension cable
Plumb bob and “C”-clamp
Meter stick
Pasco Projectile launcher
PURPOSE
A. The purpose of this laboratory activity is to
determine whether the time of flight of a ball
launched horizontally off a table on level
ground changes as the initial speed changes.
B. This part of the experiment is to obtain a
relationship between the launch angle and
horizontal range.
THEORY
A. When a ball is launched horizontally, the initial velocity has no vertical component. The
vertical displacement of the flight is given by
Therefore, the time for a ball launched horizontally depends only on the vertical distance it
travels, regardless the initial speed.
You can find time it takes for the flight,
√ , and measure horizontal range, R, and then
the initial speed is found from this relationship:
B. If the ball is shot off the table onto the floor with an angle, the time of flight is found using
the equation for the vertical motion:
(
)
→
√(
)
The range is the horizontal distance, R, between the muzzle of the launcher and the place
where the ball hits.
(
)
1
By setting the launch angle, knowing the time of the flight, and the initial height, h, we can
calculate the range, and then compare with the measured range using meter stick.
PROCEDURE
You need to determine the initial speed that the launcher will shot with by launch horizontally.
Using the projectile's horizontal distance and the height, you can calculate the initial speed.
You can use any of the ranges, but once you decide to use a particular range, keep that range
for the rest of your data taking. This gives you the initial speed for your experiment in part B.
Part A
1. Secure the launcher at the end of your table. Adjust the launch angle to be zero. Pick a
launch range (long, medium, and short). Load a ball, then launch. Note where the ball is
landed. And then put a carbon paper on top of a white paper and tape it down.
2. Reload the ball make few shots. Record the measured average R using meter stick,
measure h, the vertical distance from where the ball is launched to floor.
3. Repeat with another range. Fill out the data table, calculate the initial speed.
4. Decide which launch range you will use in part B.
Part B
1. Adjust the angle of the projectile launcher to the angle that your instructor given to you.
2. Put carbon paper on top of a white paper and tape it down to secure. Measure the
horizontal distance from the muzzle to the edge of the paper.
3. Load the using the range you decided in part A. Fire. Fire few times.
4. Look at the carbon paper, estimate the average landing spot. Measure horizontal distance
R.
5. Repeat step 2 to 4, until you have at least 3 angles.
6. Use angle, h, calculate time in flight, vo and then calculate R you expect it to be.
Compare with the measured R. Find the ratio of Rmeasured to Rexpected. Find % error.
Pre-lab Calculation
If R and h are measured as indicated in the table, find the time of flight, and the initial launch speed.
Now use this speed, to fill out the second table.
Launch angle
0
Launch angle
o
25
measured R
measured h
2.20 (m)
1.00 (m)
measured h
1.00 m
Time in flight
Time in flight
Measured R
3.00 m
Expected R
initial speed
Ratio(Rm/RE)
2
Thing about the QUESTIONS in your conclusion
1. How do the values for the time of flight for the short, middle, and long range distances
compare when the ball was launched horizontally?
2. Can you conclude from the above table that the time for a ball launched horizontally is
independent of the initial speed?
3. Why would time of flight depend on the angle of the launch?
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