SI

ENERGY TYPES AND TRANSFORMATIONS

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 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.

CHEMICAL ENERGY

• When bonds break they release energy; you get this energy when you eat and digest food.

• Plants use photosynthesis to turn light 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 a nucleus).

• Both cause a small amount of mass to be converted to a large amount of energy (E=mc2).

• This occurs in nuclear reactors, nuclear bombs, and stars.

ELECTRICAL ENERGY

• 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 a substance has because of its temperature

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

OBJECT BEING LIFTED BY A CRANE