Swinging Pendulum

Overview

This activity demonstrates how potential energy (PE) can be converted to kinetic energy (KE) and back again. Given a pendulum height, students calculate and predict how fast the pendulum will swing by understanding conservation of energy and using the equations for PE and KE. The equations are justified as students experimentally measure the speed of the pendulum and compare theory with reality.

Engineering Connection

Mechanical engineers design a wide range of consumer and industry devices—transportation vehicles, home appliances, computer hardware, factory equipment—that use mechanical motion. The design of equipment for demolition purposes is another example. Like the movement of a pendulum, when an enormous wrecking ball is held at a height, it possesses potential energy, and as it falls, its potential energy is converted to kinetic energy. As the wrecking ball makes contact with the structure to be destroyed, it transfers that energy to take down the structure.

NGSS Alignment

This lesson helps students prepare for these Next Generation Science Standards Performance Expectations:

• MS-PS3-5. Construct, use, and present arguments to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object.
• MS-PS3-2. Develop a model to describe that when the arrangement of objects interacting at a distance changes, different amounts of potential energy are stored in the system.

This lesson focuses on these aspects of NGSS Three Dimensional Learning:

Science & Engineering Practices	Disciplinary Core Ideas	Crosscutting Concepts
Engaging in Argument from Evidence. Construct, use, and present oral and written arguments supported by empirical evidence and scientific reasoning to support or refute an explanation or a model for a phenomenon. Scientific Knowledge is Based on Empirical Evidence. Science knowledge is based upon logical and conceptual connections between evidence and explanations. Developing and Using Models. Develop a model to describe unobservable mechanisms.	PS3.C: Relationship Between Energy and Forces. When the motion energy of an object changes, there is inevitably some other change in energy at the same time. When two objects interact, each one exerts a force on the other that can cause energy to be transferred to or from the object. PS3.A: Definitions of Energy. A system of objects may also contain stored (potential) energy, depending on their relative positions.	Energy and Matter. Energy may take different forms (e.g. energy in fields, thermal energy, energy of motion). Systems and System Models. Models can be used to represent systems and their interactions—such as inputs, processes and outputs—and energy and matter flows within systems.