Energy Types and Transformations

1. Energy Types and Transformations SI

2. How are work and energy related? • When work is done, energy is transferredto an object (or system). • Energy is the capacity (or ability) to do work. • Ex) pulling back on a sling shot, your hand does workon the elastic and transfers energyto it.

3. How is energy measured? • The amount of energy transferred is measured by how much workis done on the object. • Energy and work are both measured in Joules (J); the calorie is another unit of energy.

4. Potential Energy • Also known as, storedenergy. • Energy an object has because of its position.

5. Elastic potential energy • Energy that is stored in any type of elastic material (rubber bands, bungee cords) • Ex) the energy stored in the stretched rubber band of the slingshot before it is released; it can do work later (stored energy).

6. Gravitational potential energy • Energy related to an object’s vertical position; resulting from the gravitational attraction between two objects. • Ex) a book on top of a table; a car at the top of a hill • gravitational potential energy depends on: mass, height, and acceleration due gravity • Equation: P.E.= mx g x h

7. Gravitational Potential Energy • Remember, free-fall acceleration due to gravity (g) on Earth is 9.8 m/s2. • Because mass x gravity is equal to weight or force (measured in Newtons) the equation for P.E. is like work=Fxd; the distance for P.E. is actually height (h).

8. Kinetic Energy • Energy of a movingobject due to the object’s velocity. • K.E. depends upon: massand velocity(or speed). • Equation: K.E.= ½x mx v2 • *only the velocity number gets squared! • K.E. depends more on the velocity than on the mass. Why? Think about car crashes at higher speeds!! Double the speed = quadruple the energy. (mass of the car is constant)

9. Mechanical Energy • Amount of workan object can do because of its kinetic and potential energies. • The sum of the P.E. and K.E. in a system. • Can see it, either because of the object’s motion or because of its position.

10. Nonmechanical Energy • Energy that lies at the level of the atomsthat does not affect the motion of the object on a large scale or in the bigger picture; can’t observe it directly, but you know it is there. • Remember the kinetic theory of matter; atoms and molecules are constantly in motion.

11. Chemical Energy • Amount of energy in an object in relation to the positionof the atoms it contains. • A form of potential energy • When bonds break they release the stored energy (P.E.); you get this energy when you eat and digest food. • Plants use photosynthesis to turn sunlight energy into chemical energy. This energy is trapped in the bonds of the food.

12. Nuclear Energy • Energy released during nuclear fusion(combining the nuclei of 2 or more atoms) and nuclear fission(splitting of an atom nucleus). • Both cause a small amount of mass to be converted to a large amount of energy (E=mc2). • Also a type of P.E. stored in the nucleus of the atom. • This occurs in nuclear reactors, nuclear bombs, and stars.

13. Electrical Energy (Electricity) • Energy from the flow of electronsthrough wires or other conducting materials.

14. Light • Can carry energy across emptyspace (a vacuum) in the form of electromagneticwaves.

15. Thermal Energy • Energy that is created using heat • Examples: heat from a fire, boiling pot of water

16. Law of Conservation of Energy • Energy can not be created nor destroyed, it can only change forms • Example: • Dropping an object: potential  kinetic • Windmill turning: kinetic  electrical