# 玩微信红包扫雷有猫腻

Science class online
Chemistry and physics lessons

# Mechanics

Free online mechanics lesson for elementary school,  middle school and high school.

 Science class Chemistry Electricity Optics Mechanics Mechanics lessons Gravity - The solar system - motions of celestial bodies - Physical interactions - Effects of gravity - Weight of an object - Difference between weight and mass - Relationship between weight and mass  Energy - Energy basics - Potential energy - Kinetic energy - Mechanical energy - Translational Kinetic Energy - kinetic energy mass and speed

 _____________________________________________________   _____________________________________________________

## Gravity

### Energy basics

 1) What is energy ? The concept of energy is linked to various situations but it can be defined as follows: An object owns energy if it can acts on itself or on another object. In this definition " to act " means there can be modifications of: - shape - trajectory - speed - position - température - pressure - chemical composition - electrical state - magnetical state etc ______________________________________ ______________________________________ 2) Main types of energy main forms of energy are: - Kynetic energy (motion energy) - Potential energy ( position energy ) - Chemical energy  - The light energy  - Electrical energy - heat energy 3) Transfers and energy conversions When an object gives a part of its energy to another object there is an energy transfer. When energy changes its form, there is an energy conversion. Lorsque l'énergie d'un corps est transmise à d'autres corps on parle alors de transfert d'énergie. Lorsque l'énergie d'un corps change de forme on parle alors de conversion d'énergie. Talking about chemical transformations, the french chemist Lavoisier established a simple rule: " Nothing is lost, nothing is created, everything is transformed " This rule also applies for energy: - If an object's energy decreases it isn't lost: this energy is transfered to another object or converted in another type of energy. - If an object's energy increases it is not created from nothing: this energy comes from another object, or results from an energy conversion. To sum up, every energy change can be explained by a transfer or a conversion. ______________________________________ ______________________________________
____________________________________

____________________________________