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