Mr Poe Test 3

Energy

The ability to cause change

Kinetic Energy

Energy of motion

Potential Energy

Stored energy that can be converted into kinetic energy

Elastic Potential Energy

Energy stored by things that stretch or compress

Chemical Potential Energy

Energy stored in chemical bonds

Gravitational Potential Energy

Stored energy caused by gravity

Mechanical Energy

The sum of kinetic and potential energy

Conservation of Energy

Energy cannot be created or destroyed, only changed

Kinetic Energy Formula

$$KE = \frac{1}{2}mv^2$$

Gravitational Potential Energy Formula

$$GPE = mgh$$

Mechanical Energy Formula

$$ME = KE + PE$$

Work Formula

$$W = F \times d$$

Power Formula

$$P = \frac{W}{t}$$

Specific Heat Formula

$$Q = mc\Delta T$$

Work

Change in energy caused by a force acting over a distance

Power

The rate at which work is done

Mechanical Advantage

How much a machine multiplies the force supplied

Heat

Thermal energy flowing from high temperature to low temperature

Temperature

The average kinetic energy of particles

Conduction

Heat transfer between objects that are physically touching

Convection

Heat transfer caused by movement of particles in a liquid or gas

Radiation

Energy transfer through electromagnetic waves

Conductor

An object that conducts heat well

Insulator

An object that does not allow heat to flow easily

Best Conductors

Silver, copper, and aluminum

If Potential Energy Increases

Kinetic energy decreases

If Potential Energy Decreases

Kinetic energy increases

Fuel → Car Engine

Chemical potential → thermal + kinetic

Light → Plants

Radiant → chemical potential

Electrical → Light Bulb

Electrical → thermal + radiant

Electrical → Radio

Electrical → sound

Electrical → Blender

Electrical → kinetic + sound

Work Unit

Joule ($J$)

Power Unit

Watt ($W$)

Force Unit

Newton ($N$)

Time Unit

Second ($s$)

Mass Unit

Kilogram ($kg$)

Distance Unit

Meter ($m$)

KE Variables

$m$ = mass, $v$ = velocity

GPE Variables

$m$ = mass, $g$ = gravity ($9.8\,m/s^2$), $h$ = height

Work Variables

$F$ = force, $d$ = distance

Power Variables

$W$ = work, $t$ = time

Heat Transfer Types

Conduction, convection, radiation

Work Example

$$50\,N \times 6\,m = 300\,J$$

Power Example

$$500\,J \div 10\,s = 50\,W$$

GPE Example

$$10\,kg \times 9.8\,m/s^2 \times 5\,m = 490\,J$$

KE Example

$$\frac{1}{2} \times 2\,kg \times (6\,m/s)^2 = 36\,J$$

Energy Change in a System

Energy can be introduced, forces/work can be applied, or energy can leave the system

Causes of Kinetic Energy Loss

Friction (converts kinetic energy into heat) and loss through sound

Conditions for Work to Occur

A force must be applied over a distance, and the force must be in the same direction as the distance moved

Energy in a Closed System

Total energy stays the same; energy can change forms but cannot be created or destroyed

Why Fluffy Materials Are Good Insulators

They contain trapped air pockets, and air is a poor heat conductor