Energy What is energy?

Energy comes in many forms that we are familiar with. Definition: energy – a measure of the ability to do work. Energy is measured in Joules (J) Hey… Work has the same unit as energy! Light Sound Heat

Sound Energy Light Energy Thermal & Light Energy

Energy Energy comes in many forms… Definition: mechanical energy – energy that can be used to do physical work. Examples: Sound Waves Objects in Motion (kinetic) Definition: chemical energy – energy stored in the bonds of atoms. Burning Gasoline Batteries Food

Energy Definition: electrical energy – energy resulting from the flow of electrons. Examples: Electricity Lightning Definition: radiant energy – energy travelling as electromagnetic waves. Sunlight Heat

Energy is very closely related to work. In fact… Energy must be transferred to do work! It takes energy to do pretty much anything. Energy is constantly flowing through the universe.

When you pull a rubber band back, you are doing work on the rubber band. By doing that work, you are transferring some of your energy into the rubber band. You used energy to do the work that stretched the rubber band! Now, the rubber band has the energy you used!

Mechanical Energy comes in 2 Great-Tasting Flavors! Potential KINETIC

Potential Energy When you stretched the rubber band, the energy you transferred to it was held as “potential energy”… Definition: potential energy – the stored energy that results from an object’s position or condition.

Potential Energy When an object is stretched or compressed, it has “elastic” potential energy.

Potential Energy When an object is above the ground, it has “gravitational” potential energy. We will focus on GPE.

Gravitational Potential Energy GPE depends on mass and height of an object. The GPE equation: PE = mgh m = mass (kg) g = gravitational acceleration (9.8 m/s2) h = height (m)

GPE at Work

Only MOVING objects have kinetic energy! In the example with the rubber band…after you released the rubber band… It had kinetic energy as it snapped back into place. Definition: kinetic energy – the energy an object has because of its motion. Only MOVING objects have kinetic energy! What would happen to a bottle cap if the rubber band hit it?

Kinetic Energy OMG!!! Kinetic Energy!

The kinetic energy equation: KE = ½ mv2 m = mass (kg) v = velocity (m/s) Higher velocity gives increases your KE more than a higher mass. This is because velocity is squared!

Did the energy disappear, or did it just change into other forms…? What happens to energy?? When you hit a baseball, what happens to the energy that you transferred to the bat? Did the energy disappear, or did it just change into other forms…?

The baseball flies away! What happens to energy?? When you hit the baseball, the kinetic energy of the swinging bat is transferred to the baseball. The baseball flies away!

What happens to energy?? Energy is also used to produce the cracking sound.. And some energy is used to heat up the bat and the baseball!

The Law of Conservation of Energy. What happens to energy?? What happened with the baseball is an example of a very important law… The Law of Conservation of Energy.

It is always transferred. The Law of Conservation of Energy states: ENERGY CAN NEVER BE CREATED OR DESTROYED. It is always transferred.

Energy can change forms!

What point has the most PE? What about the most KE?