Download 3.3.2 kinetic potential energy

Derive and use the equation for gravitational
potential energy close to the Earth’s surface.
 Use the equation for kinetic energy.
 Solve problems involving exchange between
kinetic and gravitational potential energy.
 Apply the principle of conservation of energy
to determine the speed of an object falling.

You should make sure you learn the definitions and
understand what they mean.
There are many different forms of energy and you should be
able to name a few without too much trouble for example….
Kinetic
Sound
Light
Thermal
Gravitational
Electrical
Energy
Strain/Elastic
Nuclear
Chemical
However what is energy?
Energy is the ability to do work
Whenever energy is changed from one form
to another work is said to be done.
For example a car converts chemical energy in the fuel air
mixture into movement energy of the car.
Energy in food allows you to run, skip, hop and jump merrily
around.
The strain energy stored in a long bow allowed the English
archers to fire arrows at the French from great distances at
the battle of Agincourt.
There are some we are not so interested in but it is worth
your while knowing what they involve.
Strain/Elastic Energy
Light Energy
Due to the deformation of Due to the electromagnetic field
the bonds between atoms in disturbances that transfer energy
the object.
from one place to another.
Really the distortion causes
work to be done against
electrostatic forces.
Energy is stored in the
stretched bonds hence it is
normally termed Elastic
Energy.
Nuclear Energy
Due to the strong and weak
forces between the particles in
the nucleus of a substance.
Thermal Energy
Chemical Energy
Due to the making and breaking
of bonds between atoms in
substances. Electromagnetic
potential due to the
arrangement of charges
determines this form of energy.
The bonds have energy stored in
them and when bonds are made
energy is given out but energy is
needed in order to break them!
Why do we need a match to
start a fire??
Due to the internal energy
of a material which is
linked to the Kinetic Energy
of the atoms in it.
The hotter a substance the
more Kinetic Energy they
have.
Sound Energy
Due to the Kinetic energy of
the particles in the material
transferring the sound. They
rely on electrostatic forces to
make each particles move
Gravitational Potential Energy
The two types
of energy we
need to be able
to calculate
are……
The energy a body has by virtue of it’s
position.
The amount of energy depends on the
mass, gravitational field strength and
the height change from the initial
position.
Kinetic Energy
The energy a body has by
virtue of it’s motion.
The amount of energy
depends on the mass and
velocity of the object.
Felix Baumgartner's
supersonic freefall
Potential Energy can refer to any form of energy that is a
store such as Chemical Potential Energy, Gravitational
Potential Energy, Elastic Potential Energy.
It means the energy is stored and waiting to be released
just like an object on a shelf, once caused to move off the
shelf it can change the Potential energy → Kinetic energy.
If an object is lifted you lose energy by doing work in your
muscles and turn it into Gravitational Potential Energy as
you do work against the pull of Gravity.
It is referred to as Gravitational Potential Energy
since the forces you are working against are
Gravitational.
Gravitational Potential Energy
When lifting an object work has to be
done against the force of Gravity.
TESCO
The force is called the Weight = mg
Value
Beans
As we already know
mg
Work done = Force * distance moved
(in direction of the force - vertically.)
Therefore… … …
h
TESCO
Value
Beans
Gravitational Potential Energy = mgh
Kinetic Energy
When causing an object to
accelerate work has to be done.
The force
v2
F = ma or a = F/m
TESCO
Value
Beans
m
As we already know
v2 = u2 + 2ax
Therefore since u = 0… … …
and Energy or Work Done = Fx
v2 = 2xF/m
Fx = ½mv2
Kinetic Energy = 1/2mv2

 WEP
Support
 S&C Escalator
 Practical 5.3 – Investigating GPE