Transcript 6 Nonmechanical Energy Notes

ENERGY TYPES AND TRANSFORMATIONS
SI
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=mc 2).
• 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