Bull’s Eye Lab
Name:_____________________________________
Mod:___________
Date:___________
Pre-Lab Questions:
1. Describe what separates case 1 projectiles from others.
2. Describe what separates case 2 projectiles from others.
3. Describe what separates case 3 projectiles from others.
4. In the lab, what is the distance the ball should be rolled once it leaves the ramp and before it
rolls off the edge of the table?
5. In the lab, what is the plumb bob used for?
6. In the lab, what variable you are supposed to be solving for?
7. In the lab, when is the ball supposed to hit the ground? Who should be present before the ball
touches the ground?
Purpose:
- To predict where an object will land the on the ground using the kinematic equations for
projectiles when given an initial horizontal velocity.
Theory:
In a case 1 projectile, an object is launched with some initial height an angle of zero degrees
above the horizontal. Therefore the initial velocity of the object will be directly in the horizontal
direction and the initial velocity in the vertical direction will be zero. For case 1 projectiles this means
that an object that is dropped at the same height as an object that is launched horizontally will hit the
ground at the same exact time. The displacement of the object when it completes it projectile path with
have a negative displacement in the vertical direction, because the final position is below the origin.
Here are the equations used to solve for projectile motion problems, which are formulated from the
kinematic equations.
1
𝑣𝑖𝑥 = 𝑣𝑓𝑥
𝑑𝑦 = 𝑣𝑖𝑦 𝑡 + 2𝑔𝑡 2
𝑑𝑥 = 𝑣𝑖𝑥 𝑡
𝑣𝑓𝑦 = 𝑣𝑖𝑦 + 𝑔𝑡
𝑣𝑓𝑦 2 = 𝑣𝑖𝑦 2 + 2𝑔𝑑𝑦
Materials List:
- Steel Ball
- Tape
- Carbon Paper
- Marker
- Bull’s Eye Target
- Plumb Bob
- Ramp
- Stop watch
- Meter Stick
Procedure:
1. Set up a ramp with a small incline. Make sure the end of the ramp is exactly 75.0 centimeters
from the end of the table top.
2. Place your steel ball on the ramp and release it so that it accelerates down the ramp. Make sure
to mark where you released the ball on the ramp so that you may replicate the same run over
again, which is needed in the next few steps.
3. Once the steel ball reaches the table top, it will continue to move with constant velocity.
Measure the time it takes for the steel ball to complete the 75.0 centimeter distance from the
end of the ramp to the edge of the table and record it in table A. Make sure that the ball does
not touch the floor, so have a member of the lab group catch the ball as measurements are
taken.
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4. Once the time is found, calculate the velocity of the steel ball rolling on the table top and record
it in table A. Round the velocity to the nearest thousandth place.
5. Complete steps 2 through 4 again to collect a total of 10 velocity runs. Once they are all
collected, find the average velocity of the steel ball. This will be the initial horizontal velocity of
the steel ball when it rolls off the table. Record the initial horizontal velocity (Vix)in Table B:
Table A:
Trial Number
1
2
3
4
5
6
7
8
9
10
Average
Distance (m)
Time (sec)
Velocity (m/s)
6. Measure the height of the table from the floor to the top edge of the table where the ball will
roll off. This is the height in the y-direction (dy) and record it in Table B:
7. Find the point where the ball was rolling off the edge of the table and attach the plumb bob to
that location. Hang the plumb bob just so that the plumb bob is barely hanging above the floor.
This point on the ground is where the horizontal displacement is measured from when
determining the drop zone on the ground. Place a piece of tape at the location directly under
the plumb bob and mark it.
Table B:
Vix =
t=
dx =
Viy =
Vfy =
g=
t=
dy =
8. Solve for the drop zone of the ball using the projectile motion equations and the information
that has been collected in Table B. Solve for “dx” in Table B making sure to show all work!
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9. After calculating the horizontal displacement traveled by the steel ball (dx), measure that
distance out on the floor from the piece of tape you placed down marking the starting point.
Make sure that the displacement in the x-direction remains parallel to the path of the steel ball
as it rolls down the incline and through the air. Place a piece of tape where you predict the ball
will land and mark it.
10. Take your bull’s eye sheet of paper and place it on top of the drop zone where you predict the
ball to land. Place a few pieces of tape on the target so that it doesn’t move. Then place a piece
of carbon paper on top of the bull’s eye to mark the paper when the steel ball lands. Do not
tape down the carbon paper!!!
11. Once you are ready to perform the experiment. Call the teacher over to check your work and
view the results of your experiment. Do not test the experiment till the teacher is present.
12. After your trials, remove the carbon paper from the target making sure the target does not
move. Measure the horizontal displacement of the ball from the piece of tape directly under
the table to the average drop location on the bull’s eye target. Record the Measured
horizontal displacement as it will be used to solve for the percent error.
Post-Lab Questions:
1. Compare the measured range of the ball with the predicted (actual) range of the ball. Explain
what differences or similarities they may have. Calculate the percent error.
2. Describe some causes, at least 3, that might make the ball miss the target on the floor? Be
specific and explain…
3. In what ways could you correct for the errors in the experiment? Explain…
4. An object is launched from the top of a building that is 10m tall. If the velocity of the object is
35 m/s horizontally, what is the range of the object?
5. An airplane is carrying supplies to a rescue team. The plane is flying at an altitude of 1356m
with a horizontal velocity of 450 km/hr. How far ahead of the landing zone should they release
the supplies from the plane?
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