Mechanical energy is the sum of an object’s potential energy and kinetic energy. In an isolated system, energy transforms between these two forms while adhering to the law of conservation of energy. This laboratory experiment uses a simple pendulum to study these energy transformations, providing insights into the fundamental principles of mechanics.
A pendulum consists of a mass suspended from a fixed point, free to oscillate under the influence of gravity. As the pendulum swings, its energy alternates between gravitational potential energy (highest at the ends of its trajectory) and kinetic energy (maximum at the lowest point). By measuring parameters such as height and oscillation time, students can calculate and analyze these energy transformations in a controlled setup.
Educational Goals
- Understanding Energy Transformations: Students will explore how gravitational potential energy and kinetic energy interchange during the motion of a pendulum.
- Developing Experimental Skills: Through precise measurements and calculations, students will enhance their ability to collect and interpret scientific data.
- Connecting Theory to Practice: By applying theoretical equations (e.g., Ep=mgh, and Ek=(mv^2)/2), students will understand the practical implications of conservation of energy.
- Enhancing Analytical Thinking: Students will analyze how changes in variables such as initial angles impact the pendulum’s motion and energy.
- Promoting Collaboration: Working in groups, students will share responsibilities for setting up the experiment, collecting data, and interpreting results.
- Emphasizing Safety Protocols: Students will adhere to safety guidelines, ensuring proper setup and handling of equipment to avoid accidents.
By the end of this laboratory activity, students will have developed a deeper understanding of mechanical energy, improved their experimental techniques, and gained confidence in applying physics concepts to real-world scenarios.
Protocol
- Hang a clamp on the universal holder; as high as possible.
- Attach an angle protractor to the foot of the universal stand.
- On each side of the angle protractor, hang a 50cm ruler.
- Suspend a mobile rigid rod with the clamp. Allow a distance of at least 20 cm between the mass of the pendulum and the table.
- Attach a 50g lead weight to the rigid rod.
- Place the pendulum at a 15° angle from the vertical.
- Measure the initial height of the pendulum mass in relation to the table using the 50 cm rulers.
- Activate the Start button on the stopwatch, which will release the pendulum. Measure its final height at the other end of its trajectory.
- Using the stopwatch, measure the time needed for the pendulum to complete 5 full oscillations (back and forth).
- Repeat steps 6 to 9, placing the pendulum at a 30° angle from the vertical.
- Check the data collected in the results table.
Anticipated Outcomes
Potential energy
For 15 degrees:
h initial = 22,6 cm − 20,0 cm = 2,6 cm = 0,026 m
m = 50 g = 0,05 kg
g = 9,8 N/kg
Ep = ? J
Ep = mgh
Ep = 0,05 kg = 9,8 N/kg = 0,026 m
Ep = 0,011 J
For 30 degrees :
h initial =30,0 cm − 20,0 cm = 1,00 cm = 0,100 m
m = 0,05 kg g = 9,8 N/kg
Ep =? J
Ep = mgh
Ep = 0,05 kg 9,8 N/kg 0,100 m
Ep = 0,049 J
Maximal speed
For 15 degrees:
Ep = Ek = 0,011 J
m = 0,05 kg
v = ? m/s
Ek = (mv2)/2
v = (√2Ek )/m = √(2 * 0,011 J )/0.05kg= 0,66 m/s
For 30 degrees:
Ep = Ek = 0,049 J
m = 0,05 kg
v = ? m/s
Ek = (mv2)/2
v = (√2Ek )/m= √(2 * 0,049 J )/0.05kg= 1.4 m/s
Summary of Assignment by Grade Range
Grades 6-8
Focus: Introduction to pendulum motion and basic energy concepts.
- Students will observe energy transformations qualitatively and measure oscillation times.
- Emphasis will be placed on understanding the relationship between height and motion.
Expected Outcomes:
- Recognition of energy transformations in a pendulum.
- Development of basic measurement and observation skills.
- Introduction to the concepts of potential and kinetic energy.
Grades 9-10
Focus: Intermediate exploration of energy conservation and quantitative analysis.
- Students will measure heights, calculate energy values, and analyze the relationship between angle, velocity, and energy.
Expected Outcomes:
- Improved ability to apply energy equations to real-world scenarios.
- Deeper understanding of energy conservation and mechanical motion.
- Enhanced data collection and analysis skills.
Grades 11-12
Focus: Advanced analysis and synthesis of energy principles.
- Students will conduct detailed experiments, calculate energy values with precision, and evaluate their findings in comprehensive lab reports.
Expected Outcomes:
- Mastery of experimental techniques and data analysis.
- Ability to critically evaluate results and identify sources of error.
- Production of professional-quality lab reports demonstrating a clear understanding of energy transformations.
This structured approach allows students at all grade levels to engage meaningfully with the concepts of mechanical energy, developing their understanding and skills progressively.
Laboratory essentials
Instruments
Universal support
Clamp
Angle protractor
50cm rulers x2
Rigid rod
50g lead weight
Timer