Energy Types and TransformationsSI

How are work and energy related?

When work is done, energy is transferred to an object (or system).

Energy is the capacity (or ability) to do work.

Ex) pulling back on a sling shot, your hand does work on the elastic and transfers energy to it.

How is energy measured?

The amount of energy transferred is measured by how much work is done on the object.

Energy and work are both measured in Joules (J); the calorie is another unit of energy.

Potential Energy

Also known as, stored energy.

Energy an object has because of its position.

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).

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.= m x g x h

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).

Kinetic Energy

Energy of a moving object due to the object’s velocity. 

K.E. depends upon: mass and velocity (or speed).Equation: K.E.= ½ x m x 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)

Mechanical Energy

Amount of work an 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.

Nonmechanical Energy

Energy that lies at the level of the atoms that 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.

Chemical Energy

Amount of energy in an object in relation to the position of 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.

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.

Electrical Energy (Electricity)

Energy from the flow of electrons through wires or other conducting materials.

Light

Can carry energy across empty space (a vacuum) in the form of electromagnetic waves.

Thermal Energy

Energy that is created using heat

Examples: heat from a fire, boiling pot of water

Law of Conservation of Energy

Energy can not be created nor destroyed, it can only change forms

Example:Dropping an object: potential

kineticWindmill turning: kinetic

electrical