Ideas about Work and Energy
Transcript Ideas about Work and Energy
Ideas about Work
What exactly is energy?
We use this word in many different
In physics, Work means something very
Work = Force x distance where both
Force and distance are vectors.
Work = the amount of Force applied
along the direction the object is moving.
Work = Force x distance (mathematically
this is the dot product)
Work can be positive or negative.
Positive work increases the energy of an
Negative work decreases the energy of
an object (think of friction on a sliding
Types of energy
There are many types of energy………chemical,
nucular, sound, heat, etc.
For now we will mainly be talking about mechanical
forms of energy which include Kinetic Energy, Potential
Energy, and spring energy
Energy is often described as the ability to do work. It’s
a method of keeping track of “stuff” because in a
closed system energy is conserved.
Conservation of Energy: one of the main conservation
laws in science.
Types of Mechanical
Kinetic energy = ½ m v2 . This is the
energy an object has because it is
Potential Energy (gravitational) = mgh.
This is the energy an object has because
it has height and the potential to fall.
The Potential Energy of gravity is a
“conservative” form of energy.
PE is path independent, it only depends
on the starting and ending locations.
PE is always a change in energy,
meaning it has a reference point. This
reference point is the location you are
calling h = 0.
Conservation of Energy
If no external forces are acting, then the total
energy of a system does not change.
Examples of this are a 1)pendulum with no
friction or air resistance 2) roller coaster with
no friction or air resistance.
Can determine speeds and heights based on
total energy remaining constant.
Energy problems with
If an external force is acting, then Work is
done by this force.
Work can either increase the starting
energy or decrease it.