P.S. 1: Chapter 5: Energy
I. The Nature of Energy A. What is Energy? -Every change that occurs—large or small—involves energy
--energy-- the ability to do work & cause change 1.) Energy & Work --energy-- the ability to do work & cause change - When something is able to change its environment or itself, it has energy! Bill Nye - Energy
2.) Different Forms of Energy KINETIC *Motion POTENTIAL *Elastic *Chemical *Gravitational
B. Kinetic Energy --kinetic energy-- the energy a moving object has because of its motion -The kinetic energy of a moving object depends on the object’s mass and its speed -UNIT USED = Joule (J)
C. Potential Energy -Even motionless objects can have energy “unseen” energy --potential energy-- stored energy due to position
1.) Elastic Potential Energy --elastic potential energy-- energy stored by something that can stretch or compress - Stored energy of position is converted to energy of motion
Bill Nye (again) Energy
2.) Chemical Potential Energy --chemical potential energy-- energy stored in chemical bonds -When bonds are broken through chemical reactions energy is released
3.) Gravitational Potential Energy --gravitational potential energy-- energy stored by objects due to their position above Earth’s surface REMEMBER: acceleration of gravity on Earth = 9.8 m/s2
4.) Changing GPE -The GPE of an object can be increased by increasing its height above the ground -If two objects are at the same height the object with the larger mass has more gravitational potential energy
II. Conservation of Energy A. Changing Forms of Energy 1.) Transforming Electrical Energy Lightbulbs transform electrical energy into light so you can see
…some of that electrical energy transformed into thermal energy heat you can feel
2.) Transforming Chemical Energy -CAR fuel spark plug fires chemical potential energy converts into thermal energy hot gases expand thermal energy is converted into kinetic energy
B. Conversion Between Kinetic & Potential Energy --mechanical energy-- the total amount of potential and kinetic energy in a system mechanical energy = potential energy + kinetic energy RoadRunner & Coyote Physics
1.) Falling Objects Apple on a tree gravitational potential energy Apple comes loose accelerates due to gravity As it falls loses height gravitational potential energy decreases
-Potential energy transformed into kinetic energy as velocity of the apple increases NOTE: mechanical energy of the apple doesn’t change as it falls
-Potential energy that the apple loses gained back as kinetic energy… …total amount of energy remains the same! The Story of Kinetic and Potential Energy
2.) Energy Transformations in Projectile Motion -Energy transformations also occur in an object traveling in a curved path during projectile motion
NOTE: mechanical energy of the ball remains constant as it rises and falls
3.) Energy Transformations in a Swing -Ride starts with a push that gets you moving kinetic energy As swing rises you lose speed but gain height
TRANSLATION: Kinetic Energy changes to Gravitational Potential Energy! -At the top of your path potential energy is at its greatest… …as the swing accelerates downward PE changes to KE
C. Law of Conservation of Energy Law of Conservation of Energy: Energy cannot be created or destroyed (only converted from one form to another) Rube Goldberg Machines - Japan TV
- Energy transformation is at times difficult to see in some systems but it does occur! Honda Rube Goldberg Commercial - Physics in Action
1.) The Effect of Friction -Swing example you can’t swing forever- without a push or you pumping your legs back & forth- you will eventually come to a stop Kinetic Energy lost??????
NO!!! Swing’s ropes/chains rub on their hooks...air pushes on the rider Some mechanical energy of swing converted to thermal energy
2.) Converting Mass Into Energy FUSION & FISSION -Small amount of mass is transformed into a large amount of energy FUSION small particles collide to make a larger particle Nuclear Fusion Animation
FISSION large particles break apart to become smaller particles Fission Animation