Unit 9-1 What is Energy? What do you think of when you hear the word energy?

What is Energy? Energy is the ability to do work. Energy is expressed in units of joules, just like work.

Potential and Kinetic Energy Potential energy is energy an object has because of its position or condition. It is stored energy. i. Example-Pulling your arm back before you release a ball. To increase potential energy you could pull your arm back further. As mass increases, potential energy increases. As height increases, potential energy increases.

Kinetic Energy Kinetic energy is energy that is due to an object’s motion. i. Example-Ball flying through the air after you release the ball. b. As mass increases, kinetic energy increases. c. As speed increases, kinetic energy increases.

Potential or Kinetic Energy Snow on the top of a mountain. An avalanche (snow falling down a hill). A textbook sitting on a desk. A textbook falling toward the floor. A person standing on a diving board. A person swimming laps in the pool.

Potential or Kinetic Energy Snow on the top of a mountain. Potential An avalanche (snow falling down a hill). Kinetic A textbook sitting on a desk. A textbook falling toward the floor. A person standing on a diving board. A person swimming laps in the pool.

Show this video on PE and KE’s Ole’ http://www.youtube.com/watch?v=t2vnyfNK870 This one would stop when you enlarge it http://www.youtube.com/watch?v=T5WJoup-RD8  

Practice Problems http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/kineticvspotentialenergy.htm Roller Coaster Example http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_pg126_coaster/mfm05_pg126_coaster.html

Gravitational Potential Energy When you lift an object, you do work on it by lifting against gravity. You transfer energy to the object. This is gravitational potential energy. b. The formula for gravitational potential energy is: Gravitational potential energy = weight x height (GPE = W x H)

Mechanical Energy Mechanical energy is the total energy of motion and the position of an object together. b. The formula for mechanical energy is: Mechanical energy = potential energy + kinetic energy ME = PE + KE

Forms of Energy REMEMBER: SACHEML Sound energy Atomic (Nuclear) energy Chemical energy Heat (Thermal) energy Electrical energy Mechanical Energy Light Energy

Sound Energy a. Caused when an object vibrates. The sound waves transmit energy through the air. b. The sound then reaches your ears.

(Atomic) Nuclear Energy a. Comes from changes in the nucleus of an atom. b. When the nucleus of a large atom splits apart, energy is given off.

Atom

Chemical Energy The energy of a compound (from foods you eat, plants and batteries) that changes as atoms are rearranged. Food is converted to chemical energy in your body.

Thermal Energy (Heat Energy) Everything (all matter) is made of particles that are always in random motion (kinetic energy). Thermal energy is all of the kinetic energy due to the random motion of particles that make up an object. The faster the particles move, the higher the temperature, and the more thermal energy that is created. Thermal energy depends on the number of particles in an object.

Extra Info Almost all the substances round you are made up of MOLECULES. These are very tiny particles that never stop moving. As air is heated up, the molecules in it move faster. As it is cooled down, the molecules move slower. In a gas or a liquid, the molecules are able to move around freely. In a solid, the molecules are stuck together. However, they can still vibrate back and forth. As a solid is heated up, the vibrations get bigger and faster. In any substance, whether it is a solid, a liquid, or a gas, the speed of the molecules is a measure of how hot or cold it is.

Electrical Energy Electrical energy is the energy of moving electrons. Electrons are the negatively charged particles of atoms. Examples-anything that plugs into an outlet

Mechanical Energy potential energy + kinetic energy ME = PE + KE

Light Energy Light energy is produced by the vibrations of electrically charged particles. Light vibrations cause energy to be transmitted.

Quickie Quiz 1. Which type of energy has to do with heat and moving particles? Sound energy Thermal energy Chemical energy Light energy

Quickie Quiz 2. The ability to do work is: Potential energy Power Mechanical energy

Quickie Quiz 3. Which would be an example of potential energy? A car rolling down the street. A bird flying through the sky. An egg sitting on the kitchen counter. A frog jumping around.

Quickie Quiz 4. Which would be an example of chemical energy? Water in the form of steam. Plucking a guitar string. The energy of moving electrons. An apple growing on a tree.