Visual Quantum Mechanics - Energy Diagrams I - Goal - Changes in energy are a good way to describe an object’s motion

Oct 25, 2026

Uploaded by Đào

Energy Diagrams I teaches using energy instead of forces to describe motion in quantum mechanics contexts through toy-car experiments. It introduces energy diagrams by plotting potential energy and kinetic energy versus location, explaining how total energy behaves when friction is ignored. Activities guide learners to sketch speed and kinetic energy graphs, interpret energy decreases due to friction, and explore how attractive magnets alter motion and change speed and energy curves near magnet positions, focusing on qualitative analysis of curve shapes.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages20

Reading Time50 min

AccessFree to download

Goal

Introduction

Using energy to describe motion

Energy diagram for no interactions

Speed vs. location sketch

Kinetic energy vs. location sketch

Exploring interactions between attractive magnets

Experiment setup with magnets

Speed and kinetic energy changes near magnets

Name Partners Date Visual Quantum Mechanics The Next Generation Energy Diagrams I Goal Changes in energy are a good way to describe an object’s motion. Here you will construct energy diagrams for a toy car and learn how these diagrams can be useful. This technique will prepare you for similar uses of energy diagrams in quantum physics. Introduction In quantum mechanics the concept of energy is frequently used to help us describe events and motion. Instead of describing changes in motion in terms of forces and accelerations, we use changes in energy. A convenient way to describe changes in energy is to sketch a graph of the value of an object’s energy at various locations. When we create such a graph for energy, we call it an energy diagram. Using energy to describe motion is somewhat different from the typical approach. However, it is a very powerful technique that can be used for both small and large objects. To prepare you for learning about atoms and other small objects you will first describe the motion of a toy car using energy diagrams.You will see that you will be able to describe this motion without actually seeing that object or its motion. All you need to know is the energy. An example of a potential energy diagram is shown in Figure 1. On the horizontal axis is the location of the car while the vertical axis shows the value of the potential energy at each location. We shall see that we can learn a lot about the car’s motion from this diagram. @ 2000 , Physics Education Research Group , Kansas State University. Visual Quantum Mechanics is supported by the National Science Foundation under grant DUE 965288. Opinions expressed are those of the authors and not necessarily of the Foundation . ED1-1 The potential energy can arise from a variety of interactions including elastic, gravitational, chemical, etc. In this tutorial, the potential energy changes are generated with the help of magnets. However, the interactions between atoms and nuclei are of different origin.Therefore, the comparison with the atom that you will attempt later on will only be concerned with the shape of the potential energy curve, not with the origin of the interactions. A. Energy Diagram for No Interactions In this activity you will arrange magnets along a track and observe the interaction between these magnets and a magnet on the car. By changing configurations ofthe magnets along the track you will obtain potential energy diagrams of various shapes.You will begin with the magnets in attractive mode. In this activity we will frequently make approximate sketches of the energy of the toy car. As a first example, consider what happens when you push the car along the track with no magnets near the track or on the car. Try it now by giving the car a gentle push. A-1. Use your observation of the motion and sketch a graph of speed vs. location.Your graph should be just a rough sketch. We do not measure the values of the speed, so we can only approximate the shape of the graph. ED1-2 A-2 . Now, sketch a rough graph of the kinetic energy vs. location. (Hint: The kinetic energy is proportional to speed2.) Again, we have not measured the kinetic energy, so we can not put values on the vertical axis, but we can learn a lot from the shape of the curve. For example, your curve probably shows that the kinetic energy decreases with distance.This result tells us that the car’s energy decreases as it moves along the track. That is not a surprise, because the car has internal friction as well as friction with the track.Your graph gives you an idea about the rate at which the friction changes the speed. The friction between the wheels of the car and the track is relatively high. If we were to account for that friction, it would have made the energy diagrams complicated. However, for the purposes of our qualitative analysis we will try to think about what would have happened if the friction acting on the car were very small. For

FAQs

Why are energy diagrams useful for describing motion in this tutorial?

They replace describing motion using forces and accelerations with tracking how an object’s energy changes with location, allowing you to infer motion behavior from the graph’s shape.

What should a speed graph and kinetic energy graph look like when there are no magnets present?

When you sketch speed vs. location and kinetic energy vs. location without measurements, the shape should indicate how the car’s energy changes; kinetic energy decreases with distance due to internal and track friction.

How do the diagrams change near attractive magnets, and what should learners record?

As the car approaches and passes magnets, speed changes significantly in the neighborhood of each magnet; learners should sketch speed and kinetic energy vs. location and indicate magnet locations on their diagrams.

Oct 25, 2026

Uploaded by Đào