ENERGY WHAT IS ENERGY ENERGY is

ENERGY

WHAT IS ENERGY? • ENERGY is the ability to do work. • Energy has two main forms, -KINETIC ENERGY -POTENTIAL ENERGY • ENERGY is measured in units called JOULES • LAW OF CONSERVATION OF ENERGY: Energy cannot be created or destroyed, only transformed from one form to another.

POTENTIAL ENERGY • POTENTIAL ENERGY is energy stored based on position or chemical composition. • The amount of potential energy associated with an object depends on its position. • Two types of potential: gravitational and elastic • What are some examples?

CALCULATIONS • FORMULAS: P. E. = Weight x Height (Weight = Mass x Gravity) • SI UNIT: Joule (J)

PRACTICE 1. A hiker climbs 50 m up a hill. He weighs 500 N. How much gravitational potential energy does he have at the top of the hill? 2. Richard wants to know how much potential energy his cat has when it climbs to the top of the tree near his house. The tree is 10 m high, and the cat has a mass of 1 kg. Gravity is 9. 8 m/s 2. How much potential energy does the cat have?

KINETIC ENERGY • KINETIC ENERGY is energy of motion. • The amount of kinetic energy associated with an object depends on mass and velocity (speed) of the moving object. • What are some examples?

CALCULATIONS • FORMULA: K. E. = mass x velocity 2 2 • SI UNIT: Joule (J)

PRACTICE Calculate the kinetic energy of the wagons • A) A 10 kg wagon moves at 5 m/s. What is its kinetic energy? • B) A 20 kg wagon moves at 5 m/s. What is its kinetic energy? • C) A 10 kg wagon moves at 10 m/s. What is its kinetic energy? *What do you notice about the K. E. when the mass is doubled? *What do you notice about the K. E. when the velocity is doubled?

Example of Energy Transformation