ENERGY

ENERGY IS THE ABILITY TO DO WORK describes a system’s ability to cause change. A system that has energy has the ability to do work. ENERGY IS THE ABILITY TO DO WORK

is the S.I. unit of measurement for energy. Pushing a 1-kilogram object with a force of one newton for a distance of one meter uses one joule of energy. A joule (J) is the S.I. unit of measurement for energy.

One joule is a pretty small amount of energy. An ordinary 100 watt electric light bulb uses 100 joules of energy every second!

Systems or objects with potential energy are able to exert forces (exchange energy) as they change. Potential energy is energy due to position.

Potential Energy Objects that have potential energy do not use the energy until they move. An object’s potential energy comes from the gravity of Earth. Technically, energy from height is called gravitational potential energy. Other forms of potential energy also exist.

Potential Energy Ep = mgh Mass (kg) Potential Energy (joules) Height (m) Acceleration of gravity (m/sec2)

Energy of motion is called kinetic energy. A moving cart has kinetic energy because it can hit another object (like clay) and cause change.

Kinetic Energy Energy of motion is called kinetic energy. The kinetic energy of a moving object depends on two things: mass and speed. Kinetic energy is proportional to mass.

Kinetic Energy EK = ½ mv2 KE (joules) mass of object (kg) velocity (m/sec)

Mathematically, kinetic energy increases as the square of speed. If the speed of an object doubles, its kinetic energy increases four times (mass is constant).

Types of energy POTENTIAL ENERGY

is a form of energy stored in molecules. TYPES OF ENERGY Chemical energy is a form of energy stored in molecules. Batteries are storage devices for chemical energy.

Elastic Energy is stored by stretching or compressing

Electrical energy (static) comes from the build up of charges. TYPES OF ENERGY Electrical energy (static) comes from the build up of charges.

Gravitational Energy is stored due to an object’s position and mass

is a form of energy stored in the nuclei of atoms. TYPES OF ENERGY Nuclear energy is a form of energy stored in the nuclei of atoms. In the Sun, nuclear energy stored in the nucleus of Hydrogen atoms and is transformed to heat

Types of Energy KINETIC ENERGY

Electrical energy (current) comes from electric charge, TYPES OF ENERGY Electrical energy (current) comes from electric charge, which is one of the fundamental properties of all matter.

is energy that is carried by electromagnetic waves. TYPES OF ENERGY Light energy is energy that is carried by electromagnetic waves.

TYPES OF ENERGY Motion (kinetic) is the energy caused by the movement of an object from one place to another

Sound energy is transferred by the vibration of an object

Thermal energy is transferred from a hot object to a cold object

Sources of energy The chemical potential energy stored in the food you eat is converted into simple sugars that are burned as your muscles work against gravity as you move.

Systems change as energy flows and changes from one part of the system to another. Each change transfers energy or transforms energy from one form to another.

The workings of the universe can be viewed as energy flowing from one place to another and changing back and forth from one form to another.

Kinetic energy becomes important in calculating braking distance.

No new energy is created no existing energy is destroyed. As energy takes different forms and changes things by doing work, nature keeps perfect track of the total. No new energy is created and no existing energy is destroyed.

Conservation of Energy The idea that energy transforms from one form into another without a change in the total amount is called the law of conservation of energy. The law of energy conservation says the total energy before the change equals the total energy after it.

The conservation of energy is most useful when it is applied to a closed system. Because of the conservation of energy, the total amount of matter and energy in your system stays the same forever.

How can we predict how energy will change? One thing we can always be sure of is that systems tend to move from higher to lower energy.

The total energy in the system is the potential energy of the ball at the start. Later, the ball is at a lower height (h) moving with speed (v) and has both potential and kinetic energy.

When you throw a ball in the air, the energy transforms from kinetic to potential and then back to kinetic.

The word work has a very specific meaning. Work is the transfer of energy that results from applying a force over a distance. Work (joules) = Force (newtons) distance (meters) W = F d

That means 90% of the energy is released as wasted heat. Regular (incandescent) light bulbs convert only 10% of electrical energy to light. That means 90% of the energy is released as wasted heat.

Flow of Energy