Unit III Energy

Physical Science Forms of Energy

Energy is the ability to do work• Measured in Joules (J) just like work• All matter has energy

General Forms of Energy1. Kinetic Energy: KE = ½ m v2

The energy of motion. Anything that is moving has kinetic energy.

Do these people have KE?

2. Potential Energy: PE = mghEnergy that is stored or is not being used yet

Do these things have PE?

How to change KE• Change the mass

or velocity of an object

• If velocity is doubled, KE is quadrupled

Types of PEGravitational PE: depends on how high

off the ground an object is. * the greater the height and mass the object has the more Gravitational PE it has

Elastic PE: the ability of an object to rebound to its original shape or size

(we don’t have to calculate this one)

Types of Energy1. Mechanical:

Energy of everyday objects (anything with mass and volume)

2. Chemical Energy: energy that is stored in chemical bonds

3. Electromagnetic Energy: energy that is related

to charge and magnetic poles

4. Thermal Energy: energy that is based on the internal motion of particles in an object(Heat and temperature)

5. Nuclear Energy: energy that is contained in the nucleus. Released when strong and weak nuclear forces are overcome

Energy Conversion• When energy is transferred

between one type and another.

Example: burning gasoline transfers chemical potential into thermal energy

Energy Conversion• In a perfect situation, the total

energy in a conversion is conserved.

• Total Energy is all of the PE and KE of a situation added together.

•KE1 + PE1 = KE2 + PE2

KE and Friction• Friction slows an object down

therefore it reduces the amount of kinetic energy

• Increases the amount of Thermal Energy

Practice Problem1. A 0.15 kg ball is

thrown into the air and rises to a height of 20.0 m. How much kinetic energy did the ball have initially?

2. A 1.25 kg steel ball with a kinetic energy of 0.25 J rolls along a horizontal track. How high up an inclined track will the ball roll if friction can be ignored?

Renewable vs. Non Renewable

• Renewable: forms of energy that can reproduce fast enough with use

• Nonrenewable: energy that cannot reproduce itself