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.

Potential energy = 50 JKinetic energy = 0 J

1.

2. Potential energy = 25 JKinetic energy = 25 J

3. Potential energy = 0 JKinetic 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