http://www.youtube.com/watch?v=Ccs92nVjc8k

The Law of Conservation of Energy

» Energy cannot be created or destroyed! » Energy is transformed from one form to another

» The sun radiates energy in the form of waves, plants transform this energy into chemical energy, then animals eat these plants and use this energy for kinetic energy.

» There are two categories which all forms of energy and be put in

Kinetic Energy and Potential Energy

Kinetic Energy» The energy of motion» Depends on mass and velocity

» There are many forms of motion:˃ Objects (people moving, falling rocks, planets

revolving)˃ Waves (light waves, microwaves, Ultra Violet)˃ Electrons (flowing through a wire, revolving around

an atom)˃ Atoms (vibrating due to temperature)

Mass and Velocity» Velocity- rate of change of displacement˃ Measures how an objects position changes over

time˃ Distance divided by time (m/s)˃ Meters per second

» Mass- quantity of matter in an object.˃ Measured in kilogram (kg) kilograms

A baby has a ball and rolls it across the ground

The ball’s mass is 3 kg

The ball is moving at 2 m/s. What is the ball’s total energy?

A rolling ball

» Mass= 3 kg (kilograms)» Velocity = 2 m/s (meters per second)

Kinetic energy = 1/2mv² = mass X volume²

(3kg)(2m/s)²

= 6 kg*m²/s²

metersseconds

2

Potential Energy» Stored energy and the energy of position» There are 2 types of potential energy˃ Gravitational Potential Energy

˃ Elastic Potential Energy (springs, rubber bands)

» Gravitational Potential Energy = mgh (mass x acceleration due to gravity x objects height)

Acceleration due to gravity = 9.8 m/s²

A baby rolls a ball example extended:» Mass= 3kg» Gravity = 9.8 m/s²» Height = ?

» What is the balls potential energy?

» What is the balls total energy? (KE + PE = Total Energy)

Think about a 3 kg ball being thrown straight up in the air. When the ball is released it only has kinetic energy.

• What is the velocity of the ball when it reaches its highest point?

• Does the ball have any kinetic energy at the highest point?

Once the 3 kg ball reaches its highest point it is 10 meters above the ground. What is the balls potential energy at this point? (mgh, mass x gravity x height = Gravitational potential energy)