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Transcript of Energy
for example lifting a concrete block,
drawing back on a bow, or
pushing a wheelbarrow,
the work you have done is transformed
into some other form of energy.
Conservation of Energy
The energy the object now possess can, in turn, do work on sommething else.
Your work becomes energy and
energy is a measure of the ability to do work. The two are directly related and both are expressed using the same units ...joules.
One of the two main cateorgies of mechanical energy; Potenital Enery, PE, is stored energy.
a concreteblock resting precariously on a steel beam 30 floors above a side walk.
a fully drawn bow can launch an arrow with a relatively high speed
One of the two main categories of mechanical energy; Kinetic energy or KE is energy due to motion
a heavily loaded wheelbarrow rolling down a hill
arrow traveling toward a target
2 types of potential energy
a)Elastic Potential Energy- energy stored in an object which has been stretched, compressed,
Example- springs, rubber band, crossbow, pole
vault, diving board, bungee cord
More on kinetic energy
Any object in motion has kinetic energy,
the more kinetic energy it has,
the more diffcult it becomes to stop the object.
If we consider stopping a moving automobile,
we might easily speculate that kinetic energy will depend upon (two things)...
the mass of the object, and
how fast it is moving
Notice that Kinetic energy is more dependent upon speed than on mass.
For instance, doubling the mass of an object, doubles the KE.
However, if you double the speed...
...since the speed is squared in the equation...
...the KE is quadrupled.
Energy cannot be created or destroyed;
it may be transformed from one form to another, but the total amount of energy never changes.
While forces such as friction and air resistance, or forma of energy like heat, light, and sound, might appear to take energy from the system, in fact, the energy has simply changed form.
b)Gravitational Potential Energy- energy stored in an object because of its vertical location
Obviuosly, you do more work lifting a massive
object than you will lifting a lighter
object. And, the higher the object is
located above something the more energy the
object will possess. Likewise, the lower an
object is initially situated below some
height, the more work you do to raise it up.
Thus, gravitational PE must somehow depend on an object's weight, and it's height.