EXPERIMENT 202
CONSERVATION OF MOMENTUM: THE BALLISTIC PENDULUM
ALMANDRES, CHRISTINE JOYCE E.
Physics Department, Mapua Institute of Technology
PHY11L, A7, Group 2
Abstract
The experiment intends to complete its two central objectives. The first one is to
utilize the standards of conservation of energy and momentum in finding the velocity of the
steel ball. Through the experiment, the students will be able to put on more information about
the conceptions of conservation of momentum and how it is useful in finding out the velocity
of moving objects and even the distances. The experiment can also facilitate the students to
familiarize on how the angular displacement of an object is essential in receiving its initial
velocity. The experiment will also illustrate how the Kinetic Energy and the Gravitational
Potential Energy is connected with the conservation of momentum and while having a
collision.
The second purpose is to be able to confirm the initial velocity of the steel ball
through projectile motion. The students will not just discover how to calculate for the
velocity of the steel ball using the ballistic pendulum yet the proper utilization of projectile
launcher. The experiment will help the students be able to comprehend the relevance of the
particular laboratory formulas in solving problems relating Physics and will definitely be
helpful in learning other ideas about it. Another thing about this experiment is that it is a mere
to conduct and thus students will have the benefit of doing it.
The importance of this experiment is that it is a way of demonstrating how an
inelastic collision takes place, what are the things happening afterwards and lastly it
illustrates how fast an object in two dimensions is moving.
Introduction
A ballistic pendulum is equipment that is used to quantify the velocity of a bullet and
points up the principles implicated in conservation of energy and momentum. One of the
central fundamental principles is the notion that the total energy of a system is always
preserved. The energy can change outlines (i.e. kinetic energy, potential energy, heat, etc.),
but the total of all of these forms of energy must settle with the consistent unless energy is
added or detached from the system. This property has massive outcomes, from describing
simple projectile motion to deciding the ultimate fate of the universe. Another important
conserved quantity is momentum
Methodology
Before the experiment was essentially done, in which the ballistic pendulum with the
steel ball were tried first to avoid incidents and such since some of the students are releasing
the ball unintentionally even before the release. The projectile launcher with ballistic
pendulum was arranged away from the class and pointed directly towards a bag or chair to
prevent it from hitting anything or anyone. The level or range assigned for the group depends
on the group itself. Our group chose to work on a long range for the entire experiment.
Fig. 1, Tamping Rod
Fig. 2, Meter Stick
Fig. 3, Ballistic Pendulum
First, the angle marker on the ballistic pendulum was fixed to 0°. Since the group had
hitch making it constant at that angle, the group decided to verify first if the experiment table
is horizontally aligned and when it finally points at 0°, we started collecting the necessary
data. To get the preliminary height of the ballistic pendulum, the distance from the base to the
center of the pendulum while at the orientation point 0 is determined using the meter stick.
Fig. 4, Angle marker of ballistic pendulum orientation point of 0°
Fig. 5, Getting the preliminary and final height of the center of the ballistic pendulum using a
meter stick
The calculated velocity from the first part of the experiment was used to look ahead in
how far the ball will land horizontally and to examine it more; the group launched the ball
and knew which section it will fall. The group then put a bond paper under a carbon paper.
Attached the papers firmly which will be used to know the horizontal distance of the ball’s
end point since upon landing onto the carbon paper furthermore the ball will leave a black
spot on the bond paper. The black marks in the bond paper will give you an idea about how
far the steel ball pendulum arranged on to that angle. The final height of the pendulum was
evaluated from the base to the midpoint of the pendulum.
Fig. 6, The positioning of the attachment of the carbon and bond paper
The enlargement in height was measured by deducting the preliminary height of the
pendulum from the final height. The increase in height was used for computing the velocity
of the steel ball and the pendulum. The mass of the steel ball is used to calculate for its
velocity. The mass of the pendulum was also needed in order to compute for the velocity as
well as the additional 100 grams in it.
On the other hand, the pendulum positioned and secured in the air so that the ball can
be fired to the floor in straight direction. The spring gun was then positioned at the end of the
table. The perpendicular distance y, of the firing position which is the core of the gap of the
spring gun on the table down to the floor was measured using the meter stick
.
Fig. 7, Determining the horizontal displacement of the launched ball in five trials
Fig. 8, The five marks of the launched ball in a bond paper
These distances were traced. The average horizontal distance was then figured by
adding up all the five distances and also dividing it by five. The average horizontal distances
and the considered perpendicular height were used to figure for the velocity of the steel ball.
Results and Discussion
The first part of the experiment was all about the determination of the velocity of the
steel ball subsequent to the inelastic collision with the pendulum bob. Upon finishing the five
trials, the group intended for the average angle. Upon carrying out the data to be collected,
the group worked on the raise in height by deducting the preliminary height of the pendulum
to the final height. The group used the raise in height y, in knowing the change in potential
energy which is also said to be the velocity of the steel ball and the pendulum right after
collision. The group used the specified formulas from the laboratory instruction manual in
order to evaluate the initial velocity of the steel ball before its collision with the pendulum.
The other part is generally about verifying the figured initial velocity of the steel ball
throughout projectile motion. The group considered the vertical distance of the firing location
which is from orientation point to the floor. The velocity in the first section was used for
indicating the horizontal distance. When the ball was fired and fell to the carbon paper, it left
a dark mark that will point out the horizontal distance it enclosed after being launched. After
doing the five trials, the average of the horizontal distance was evaluated. After getting the
mean, and all the required data, the group calculated for the preliminary velocity using the
specified formulas in the laboratory guidebook.
The group worked for the percent difference of the two values of velocity. This is one
way to verify if the procedures were done appropriately so that the group will come up with
similarly related results.
Conclusion
From the executed experiment, I could say that it was a victory. By following the
steps acknowledged in the manual suitably gave us all the applicable data that are required.
We have figured correctly all that was essential for the experiment by using the suitable
formula for those.
In the first half of the experiment, we have used the principles of conservation of
energy and momentum in knowing the velocity of the steel ball using a ballistic pendulum.
Our data testifies that the conservation of energy and momentum can be used in getting the
velocity of the steel ball and pendulum bob. Since the collision was considered inelastic, the
final velocity of the two masses will be equal. This conclusion shows us that we have
completed the first goal of the experiment.
For the second half, we have certified the initial velocity of the steel ball through
projectile motion. The velocity in the first half was also used in this section for the function
of horizontal distance. There were five trials and the mean value of horizontal distance is
what we used to calculate for the preliminary velocity using the formula in the laboratory
handbook. The result we obtained is precise from the preliminary velocity we acquired from
the first half of the experiment. This only proves that we have also finished the second aim of
the experiment.
Recommendation
I believe that in terms of the mistakes made in the experiment, it is somewhat
minimal. The basis of error can be from the measurement of the vertical and horizontal
distances. Since we physically measured these factors, there is a high probability that the
measurements we got were incorrect. The percent difference we got was 3.08% which is
considered as a little difference.
Literature References
[1] Calderon, Jose C., (2000) College Physics Laboratory Manual, Mapúa Institute of
Technology, Manila: Department of Physics. (Abstract, Introduction, Methodology, Results
& Discussion and Conclusion
