What is Energy? Ch. 5---Section 1

Energy The ability to cause change Can take many different forms Kinetic - moving Potential - positional Thermal – Increases with heat Chemical – stored in bonds Radiant – light Sound – vibration of molecules Electrical – from electricity Nuclear – stored in atoms SI unit is the joule (J) Energy and work are related Energy is the ability to do work and work is the transfer of energy, therefore they are measured the same way!

Kinetic Energy (KE) The energy an object has due to its motion If an object isn’t moving it doesn’t have any KE Depends on both the mass and velocity of an object: If two objects have the same mass, the one travelling with greater velocity has more KE If two objects are travelling the same velocity, the object with greater mass has more KE

Gravitational Potential Energy (GPE) The energy an object has due to its position If an object isn’t moving, it can still have GPE Depends on both the mass of the object and it’s height above the ground: If two objects have the same mass, the one that is higher up has more GPE If two objects are positioned at the same height, the object with greater mass has more GPE KE and GPE are collectively referred to as Mechanical Energy

Potential Vs. Kinetic Energy Law of conservation of energy - energy cannot be created or destroyed. 1. Potential energy = 50 J Kinetic energy = 0 J 2. Potential energy = 25 J Kinetic energy = 25 J 3. Potential energy = 0 J Kinetic energy = 50 J

Thermal Energy The energy that all objects have that increases when the object’s temperature increases Due to the motion of molecules that make up the object Ex. A cup of boiling water has more thermal energy than a cup of cold water, which has more thermal energy than a cup of ice. Usually is the last step in all energy transformations because it is so hard to store.

Chemical Energy The energy that is stored in chemical bonds Is released when bonds between compounds are broken Examples of substances that contain chemical energy: Wood Gasoline Food

Radiant Energy (Light Energy) Energy that is carried by light Can be converted into thermal energy to warm objects Light travels at 300,000 km/s, which is fast enough to circle the Earth eight times in one second.

Sound Energy Energy that is transmitted through a medium in the form of vibrations. Is a mechanical wave – requires material to travel through…cannot travel through a vacuum (No sound in space) The denser the material, the faster sound will travel (travels fastest in solids)

Electrical Energy Energy carried by an electrical current Caused by fast moving particles These particles have charges that attract or repel each other.

Nuclear Energy Energy contained in the nucleus of an atom Can be released two ways: fission fusion