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REGENTS PHYSICS
STUDENT NOTES-ENERGY
POTENTIAL & KINETIC ENERGY
____________________ is required if you want to do any work.
Example:
Hammer driving a nail into wood.

Energy is a ______________________ quantity.

It is measured in __________________. The same unit as ______________.
----------------------------------------------------Energy can be converted into many forms.
Example:
Geothermal Energy to run a Turbine
Nuclear Energy (Radioactive Elements in Rocks)  Geothermal Energy (Steam) 

Work is done through this entire process.
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POTENTIAL ENERGY (PE)
Potential Energy is any energy that has the ___________________ to do work.
It is also call energy of _________________________ .
Examples :
We will look at a few of the above examples in more detail…
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GRAVITATIONAL POTENTIAL ENERGY
As an object moves away from the Earth, _____________ is required to move it against
the gravitational force.
Example:

The weights gain _________________________ potential energy.
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W = PE
PE = W = F d
PE = mgh

(Reference Tables)
Base Level – the point that is arbitrarily assigned a potential energy value of zero.
Example 1: A ball is lifted from the floor onto the table. The floor is assigned a
potential energy value of ________________ .
Example 2: A 2.0 kg object is raised a vertical distance of 3.0 m. What is the
resulting change in the gravitational potential energy of the object?
How much work was done in lifting the object the 3.0 meters?
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ELASTIC POTENTIAL ENERGY
Elastic Potential Energy is the energy stored in a ___________________ when it is
compressed or stretched.
The amount of Elastic Potential Energy is _____________ to the amount of
______________ required to stretch or compress the spring.
Example: Bow and Arrow
Work required to stretch the bow  Bow now has Elastic Potential Energy 
Hooke’s Law

The force required to compress or stretch a spring is NOT constant.

The more a spring has been stretched or compressed, the _______________
it is to stretch or compress it further.
Hooke’s Law – the _________________ required to keep a spring stretched or
compressed at a certain distance (x) in meters.
F = kx
(Reference Tables)
k is known as the SPRING CONSTANT

Strong springs will have a _______________ spring constant. A lot of
force is required to keep them stretched to a certain distance.
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Elastic Potential Energy Equation
PEs = ½ kx2

The Elastic Potential Energy (PEs ) of the spring is equal to the
______________ done in stretching the spring.

The AREA under the graph of the F vs x graph is equal to the Elastic
Potential Energy or the ______________ done in stretching the spring.
SAMPLE PROBLEMS:
1. Determine the potential energy stored in a spring that has a spring constant of 25
N/m when a force of 2.5 N is applied to it.
2. A spring with a spring constant of 40 N/m is stretched a distance of 0.5 m from
its original length. What force is required to keep it stretched this distance?
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KINETIC ENERGY
Kinetic Energy is energy of ________________ objects.

Like all forms of Energy, it is a _______________________ quantity.

Like all forms of Energy, it is measured in ________________ .

The formula for Kinetic Energy is…
KE = ½ mv2

(Reference Tables)
When you accelerate in your car, you are _____________________ your Kinetic
Energy.

Chemical Energy of the ___________________ is converted into
___________________ that moves the wheels that is converted into KINETIC
ENERGY of the moving car.

There has been CHANGE in the KINETIC ENERGY.
KE = ½ mvf 2 - ½ mvi 2
SAMPLE PROBLEMS:
1. Find the kinetic energy of a 4 kg object moving at 5 m/s and 10 m/s. What is the
CHANGE in kinetic energy?
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2. How much work has to be done to accelerate a 1200 kg car from rest to a speed of
2 m/s, assuming that there is no friction?
3. A new force of 5.0 N is applied to a 4.0 kg object over a distance of 6.0 m. What
is the change in the objects kinetic energy, assuming there is no friction?
(a) If the object was moving at 2.0 m/s before the force was applied, what
would be the velocity of the object AFTER the force is applied?
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LAW OF CONSERVATION OF ENERGY
“The _______________ amount of energy in a system does __________ change”.

This is true for a CLOSED SYSTEM. This means that no ______________ forces
or ____________________ work acts on the system.
EXAMPLE:
1. An arrow shot vertically upward from a bow.

Remember that the above example of the Conservation of Energy must be
for a CLOSED SYSTEM. What force would NOT make this a closed
system, so that energy would be lost from the system?
____________________________ !

The TOTAL ENERGY of a system must take into account friction. We call the
friction involved the ____________________ Energy of the system.

The TOTAL ENERGY (Et ) equation is…
Et = PE + KE + Q (internal energy)
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2. The swinging of a Pendulum