OWL WITH EYES LIKE THE NIGHT SKY It is one of the blessings of old friends that you can afford to be stupid with them. - RALPH WALDO EMERSON -

WHAT DO YOU NEED TO DO WORK?

TO DO WORK, YOU NEED ENERGY. ENERGY IS THE ABILITY TO DO WORK. WHEN WORK IS DONE, ENERGY IS TRANSFERRED BETWEEN SYSTEMS OR TRANSFORMED FROM ONE TYPE TO ANOTHER. ENERGY AND WORK HAVE THE SAME UNITS. IF YOU DO 6 JOULES OF WORK, 6 JOULES OF ENERGY GET SHIFTED AROUND.

ENERGY COMES IN TWO TYPES: POTENTIAL ENERGY IS STORED ENERGY. FOR SIMPLE, MECHANICAL THINGS, ENERGY CAN BE STORED TWO WAYS: 1)ELASTIC POTENTIAL ENERGY WHERE ENERGY IS STORED IN A STRETCHED OR COMPRESSED SPRING OR STRETCHED RUBBER BAND. 2)GRAVITATIONAL POTERNIAL ENERGY HAS TO DO WITH THE HEIGHT OF AN OBJECT ABOVE THE SURFACE OF EARTH

GRAVITATIONAL POTENTIAL ENERGY WOULD BE EQUAL TO THE AMOUNT OF WORK REQUIRED TO LIFT AN OBJECT TO ITS HEIGHT ABOVE THE SURFACE. YOUR WEIGHT IN POUNDS TIMES 4.4 EQUALS YOUR WEIGHT IN NEWTONS. TO GET YOUR GRAVITATIONAL POTENTIAL ENERGY ON TOP OF A ONE STORY BUILDING, MULTIPLY YOUR WEIGHT IN NEWTONS BY 4 METERS.

ANOTHER FORM OF POTENTIAL ENERGY IS CHEMICAL POTENTIAL ENERGY. THIS IS THE ENERGY STORED IN CHEMICAL BONDS. THINK ABOUT THE REACTION CH 4 + 2O 2  CO 2 + 2H 2 O ENERGY IS ALSO STORED IN ATOMIC NUCLEI. THIS WOULD BE THE SOURCE OF ENERGY IN NUCLEAR REACTIONS

SO, YOU CAN THINK OF POTENTIAL ENERGY AS ENERGY SITTING STILL OR ENERGY WAITING TO HAPPEN. THEN, THERE IS ENERGY IN MOTION – KINETIC ENERGY – ENERGY IN USE. KINETIC ENERGY DEPENDS BOTH ON MASS AND VELOCITY. THE FORMULA IS KINETIC ENERGY = ½ x m x v 2

THE TOTAL ENERGY OF A SYSTEM IS EQUAL TO ITS KINETIC ENERGY PLUS ITS POTENTIAL ENERGY. AS LONG AS NO ENERGY IS LOST OUT OF A SYSTEM, THE TOTAL ENERGY STAYS CONSTANT. THIS IS A WAY OF STATING THE LAW OF CONSERVATION OF ENERGY. ENERGY CAN CHANGE FORM, BUT THE TOTAL AMOUNT OF ENERGY STAYS THE SAME. THINK ABOUT A PENDELUM SWINGING OR A WEIGHT ATTACHED TO A SPRING.

THINK ABOUT A WEIGHT BOUNCING ON A SPRING. IT SHOULD RETURN TO THE SAME POINT EACH TIME, BUT IT DOESN’T. THINK ABOUT A PENDELUM SWINGING. IT SHOULD SWING TO THE SAME HEIGHT EACH TIME, BUT IT DOESN’T. THINK ABOUT A ROLLER COASTER CAR. WHEN IT STARTS OFF A HILL, IT SHOULD RETURN TO THE SAME HEIGHT, BUT IT DOESN’T. IF THE LAW OF CONSERVATION OF ENERGY HOLDS, WHY DO THESE THINGS HAPPEN?

ALL MACHINES ARE NOT 100% EFFICIENT, BECAUSE ENERGY CAN BE LOST THROUGH FRICTION, CONVERSION TO HEAT ENERGY, CONVERSION TO SOUND ENERGY, ETC.