Mathematics and Physical Sciences Department
GED0081L: College Physics 1 Lab
COLLEGE PHYSICS 1 LABORATORY
ACTIVITY 8
ACTIVITY 8: Conservation of Energy
8.1 Program Outcomes (POs) Addressed by the Activity
a. Ability to apply knowledge of computing fundamentals, computing specialization, and
mathematics, science, and domain knowledge appropriate for the computing models.
b. Ability to function effectively as a leader and as a member or leader in diverse teams and in
multidisciplinary settings.
c. Ability to communicate effectively with the computing community and with society at large about
complex computing activities by being able to comprehend and write effective reports, design
documentation, make effective presentations, and give and understand clear instructions.
8.2 Activity’s Intended Learning Outcomes (AILOs)
At the end of this activity, the student shall be able to:
a. Explain and solve problems involving potential and kinetic energies.
b. Differentiate potential and kinetic energies.
8.3 Objectives of the Activity
The objectives of the activity are:
a. To determine the gravitational potential and kinetic energy of an object
b. To verify the conservation of mechanical energy.
8.4 Principles of the Study
Mechanical energy is defined as the total amount of kinetic energy and potential energy of an
object that is used to do a specific work. The kinetic energy, also known as the energy of motion, of
a moving object of mass 𝑚 and speed 𝑣 can be computed using:
1
𝐾𝐸 = 𝑚𝑣 2
2
While the gravitational potential energy, of an object of mass 𝑚 held at height ℎ can be
computed by:
𝑈𝑔 = 𝑚𝑔ℎ
The unit of measure for energy is joule, named in honor of English physicist James Prescott
Joule who studied the nature of heat or thermal energy. The work 𝑊 done to displace a 1 N object to
a distance of 1 m is 1 N∙m where 1 N∙m = 1 J. The energy needed to do such work is also 1 J.
Therefore, work and energy have the same unit of measure.
Figure 9.1 Conservation of energy of a pendulum. Source: 123rf.com
Mathematics and Physical Sciences Department
GED0081L: College Physics 1 Lab
Both potential and kinetic energies are types of mechanical energy and mechanical energy
can be computed by simply adding the two.
𝑀𝐸 = 𝐾𝐸 + 𝑈𝑔
The Law of Conservation of Energy states that energy can neither be created nor destroyed,
only converted from one form to another. Hence, the potential energy of a solid object at rest, when
acted upon by a force that causes it to move, will be converted to kinetic energy.
8.5 Materials/Equipment
1 set
1 piece
1 piece
1 piece
1 piece
1 sheet
1 piece
1 meter
3 sheets
iron stand with clamps
50- gram mass
meter stick
ball
holder
carbon paper
adhesive tape
thread
white paper
8.6 Procedure
Figure 8.6 Setup
1. Place a ball on the holder as shown in Figure 8.6. Measure the distance from the bottom of the ball
to the tabletop. Denote this as H and record in Table 8.7.1.
2. Set a pendulum using a thread and a 50-gram mass tied at the end of it.
3. Raise the mass to a height h = 10 cm from the holder with the string stretched tight.
4. Release the mass from that height and allow it to hit the ball at point A as illustrated in Figure 8.6.
5. When the ball is hit, it behaves as a projectile. Note where it lands (point B).
6. Place the white paper with the carbon paper on top of it at point B and repeat the previous steps.
This time, record the horizontal distance from point B. Denote it as R and record in Table 8.7.1.
1
7. Calculate the initial speed of the ball as it leaves point A using the equation derived from 𝐻 = 2 𝑔𝑡 2
from free fall motion then 𝑡 = 𝑅/𝑣𝐴 from velocity’s formula (velocity = displacement/time).
Mathematics and Physical Sciences Department
GED0081L: College Physics 1 Lab
𝑅2𝑔
𝑣𝐴 = √
2𝐻
where R = range
g = acceleration due to gravity 9.80 m/s2
H = height
8. Using the speed obtained in step 7, compute for the kinetic energy at point A.
1
𝐾𝐸 = 𝑚𝑣 2
2
9. Compute also for the potential energy and the total mechanical energy of the ball at that position,
point A.
𝑃𝐸 = 𝑚𝑔𝐻
𝑀𝐸 = 𝐾𝐸 + 𝑃𝐸
10. Record the values in Table 8.7.2.
11. Calculate the speed of the ball when it reaches the tabletop, that is at point B, using the equation:
𝑣𝐵 = √2𝑔𝐻 + 𝑣0 2
12. Using the computed value of speed in no. 11, compute for the kinetic energy of the ball at point
B. Then compute its potential energy and mechanical energy. Record the values in Table 8.7.2.
13. Repeat steps 1-12, increasing the initial height, h, by 5 cm for each trial, until 3 sets are made.
14. Compute the percentage difference between the mechanical energies at point A and B. Record in
Table 8.7.3.
|𝐴 − 𝐵|
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 =
∗ 100
1
(𝐴
+
𝐵)
2
8.7 Data and Results
Table 8.7.1. Initial Values
Trial
h (m)
1
2
3
R (m)
H (m)
Table 8.7.2. Mechanical Energy
INITIAL
Trial
vA (m/s)
Potential
Energy
(J)
Kinetic
Energy (J)
FINAL
Mechanical
Energy(J)
vB (m/s)
Potential
Energy (J)
Kinetic
Energy (J)
Mechanical
Energy(J)
1
2
3
Table 8.7.3. Percentage Difference
INITIAL MECHANICAL
Trial
ENERGY (J)
1
2
3
FINAL MECHANICAL
ENERGY (J)
% DIFFERENCE
Mathematics and Physical Sciences Department
GED0081L: College Physics 1 Lab
8.8 Calculations
8.9 Guide Questions
1. If the speed of a particle is doubled, what happens to its kinetic energy? (b) What can be said about
the speed of a particle if the net work done on it is zero?
2. In most circumstances, the normal force acting on an object and the force of static friction do zero
work on the object. However, the reason that the work is zero is different for the two cases. Explain
why each does zero work.
3. You are working in a library, re-shelving books. You lift a book from the floor to the top shelf. The
kinetic energy of the book on the floor was zero, and the kinetic energy of the book on the top shelf is
zero, so there is no change in kinetic energy. Yet you did some work in lifting the book. Is the work–
kinetic energy theorem violated?
8.10 Discussion
8.11 Conclusion
Mathematics and Physical Sciences Department
GED0081L: College Physics 1 Lab
8.12 Credits
Created by:
Version:
Modified:
Physics Laboratory Cluster
4.0
May 2023
8.13 References
Printed References:
Hecht, Eugene (2018). College Physics, McGraw Hill Education
Serway, Raymond A. (2018). Physics for Scientists and Engineers. Cengage Learning
Serway, Raymond A. (2019). Physics for Scientists and Engineers with Modern Physics. Cengage
Learning
Szauer, Gabor (2017). Game Physics Cookbook. Packt Publishing
Wilson, Jerry D. (2019). Study Guide and Selected Solutions Manual for College Physics. Addison-Wesley
Wolf, Marilyn (2017). The Physics of Computing. Elsevier/Morgan Kaufmann
Online References:
Wolfgang, C. (2022) O.S.P Open-Source Physics. Retrieved from www.opensourcephysics.org
Duffy, Andrew (nd). Physics Simulations. Retrieved from http://physics.bu.edu/~duffy/classroom.html
Nave, Carl R. (2022), Hyper Physics. Retrieved from www.hyperphysics.phy-astr.gsu.edu
The Physics Classroom (2022). The Physics Classroom Tutorial. Retrieved from
www.physicsclassroom.com