Support for Java Applets, including Physlets, has been discontinued by browsers and Oracle. Thus, traditional *Java-based* Physlets are
no longer supported on this website. Please note Open Source Physics (OSP) Java programs continue to run on computers with Java if users
download the jar file.

The OSP team is busy updating and developing simulations using HTML5 + JavaScript.

These simulations run on almost all platforms
including tablets and cellphones. Explore the **Third Edition of Physlets Physics**
or search OSP for JavaScript to find these simulations.

# Chapter 7: Energy

Kinetic energy (KE) is proportional to the square of the speed of the object; KE is therefore a number and **not **a vector. In order to understand how to use energy correctly, we will also need to discuss isolated systems, potential energy, and internal energy.

# Table of Contents

## Illustrations

- Illustration 7.1: Choice of System.
- Illustration 7.2: Representations of Energy.
- Illustration 7.3: Potential Energy Diagrams.
- Illustration 7.4: External Forces and Energy.
- Illustration 7.5: A Block on an Incline.

## Explorations

- Exploration 7.1: Push a Cart Around.
- Exploration 7.2: Choice of Zero for Potential Energy.
- Exploration 7.3: Elastic Collision.
- Exploration 7.4: A Ball Hits a Mass Attached to a Spring.
- Exploration 7.5: Drag the Ball to Determine PE(x).
- Exploration 7.6: Different Interactions.
- Exploration 7.7: Exploring Potential Energy Functions.

## Problems

- Problem 7.1: A ball slides in a frictionless bowl.
- Problem 7.2: A 12-kg box slides up a 26.56° frictionless ramp.
- Problem 7.3: A 12-kg box slides down a 26.56° frictionless ramp.
- Problem 7.4: A 12-kg box slides down a rough ramp.
- Problem 7.5: A mass is lifted by a string.
- Problem 7.6: A modified Atwood's machine.
- Problem 7.7: Three balls are thrown off the top of a building.
- Problem 7.8: A ball is dropped on a hard floor.
- Problem 7.9: An explosive collision.
- Problem 7.10: A spring gun.
- Problem 7.11: Collision between a mass and a mass connected to a spring.
- Problem 7.12: Collision between a mass and a mass connected to a spring.