ENERGY AND ENERGY TRANSFORMATIONS What is energy and

ENERGY AND ENERGY TRANSFORMATIONS

What is energy, and what are energy transformations?

What is energy? � � Energy is the ability to cause change. Energy can cause changes in the motions of objects.

Kinetic Energy—Energy of Motion � � Kinetic energy is energy due to motion. All moving objects have kinetic energy. The faster an object moves, the more kinetic energy it has. If two objects move at the same speed, the object with more mass has more kinetic energy.

Potential Energy—Stored Energy � � � Potential energy is stored energy due to the interactions between objects or particles. The gravitational potential energy stored between an object and Earth depends on the object’s weight and height. Elastic potential energy is energy stored in objects that are compressed or stretched.

Chemical potential energy is energy stored in the chemical bonds between atoms.

In what way are all forms of potential energy the same?

Energy and Work � � Work is the transfer of energy that occurs when a force is applied over a distance. ‘Work’ is done when a force acts on an object to cause it to move, change shape, displace, or do something physical. Work depends on both force and distance. You only do work on an object if that object moves.

The girl does work on the box as she lifts it. The work she does transfers energy to the box. The colored bars show the work that the girl does (W) and the box’s potential energy (PE).

Another Example of Work: If I push a door open for my pet dog to walk in, work is done on the door (by causing it to open). But what kind of force caused the door to open?

(1) The iron hammer on its own, has no kinetic energy, but it has some potential energy (because of its weight). (2) To drive a nail into the piece of wood (which is work), he has to lift the iron hammer up, (this increases its potential energy because if its high position). (3) And force it to move at great speed downwards (now has kinetic energy) to hit the nail. The sum of the potential and kinetic energy that the hammer acquired to drive in the nail is called the Mechanical energy, which resulted in the work done.

In the 'open door' example used before, I posses potential chemical energy (energy stored in me), and by lifting my hands to push the door, my action also had kinetic energy (energy in the motion of my hands). By pushing the door, my potential and kinetic energy was transferred into mechanical energy, which caused work to be done (door opened). Here, the door gained mechanical energy, which caused the door to be displaced temporarily.

Sound Energy= The energy that sound carries When you pluck a guitar string, the string vibrates and produces sound

Thermal Energy= The sum of kinetic energy and potential energy of the particles that make up an object

Thermal energy moves from warmer objects, such as burning logs, to cooler air objects, such as _____

When you turn on a fan, there is an electric current through the fan’s motor. Electrical appliances, such as fans and dishwashers, change electric energy into other forms of energy.

• Radiant energy is sometimes called Light energy • The Sun gives off energy that travels to Earth as electromagnetic waves. • Radiant Energy-the energy that electromagnetic waves carry

Nuclear energy-energy that is stored and released in the nucleus of an atom At the center of every atom is a nucleus. In the Sun, nuclear energy is released when nuclei join together. In a nuclear power plant, nuclear energy is released when the nuclei of uranium atoms are split apart.