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Aisbet Becker, Bolwerk, Hoff, Serio, Zaporski 1
Nyssa Becker, Steph Aisbet, Cora Serio,
Kellye Zaporski, Sasha Bolwerk, and
Tessa Hoff
Energy
Thesis: There are different types of energy that can be seen and used in the world today.
I.
The Background of Energy
A. The Definition of Energy
B. Newton’s Contribution to the Field
II.
The Different Types of Energy
A. Potential Energy
B. Kinetic Energy
C. Mechanical Energy
III.
The Law of Conservation of Energy and Momentum
A. The Definition of the Law
B. Practical Examples of the Law
IV.
Friction and Gravities Effect on Energy
V.
Applications of Energy
A. To the Pendulum
B. To Newton’s Cradle
Aisbet Becker, Bolwerk, Hoff, Serio, Zaporski 2
I. The Background of Energy
Energy in early history was mainly the amount of work that humans could do. Humans
would do this alone or in large groups. Then humans continued to learn and discovered that
animals could do certain things that required abilities that humans could not necessarily do on
their own such as hauling or lifting. Because neither animals nor humans like to work, energy
conservation was strongly motivated. Energy conservation first became a thing of doing less, but
then it included finding easier ways to get work done. The invention of the wheel was an
advance in early energy conservation and fire is the oldest major source of energy. As the
conservation of energy became more advanced and people learned from previous ideas, things
such as wind power, falling or flowing water, steam machinery, and electrical power soon
became the new age of energy and energy conservation. Overall, energy is the capacity of a
physical system to do work.
Newton was a main contributor to the field of energy. His three laws impact the energy
field a great deal. Newton’s laws say that an object at rest will remain at rest unless an
unbalanced force causes it to do otherwise, an object in motion will continue in motion in a
straight line with constant speed unless an unbalanced force causes it to do otherwise, the rate at
which an object changes its velocity depends on how much force is used and how much mass an
object has, and finally for every action there is an equal reaction.
Aisbet Becker, Bolwerk, Hoff, Serio, Zaporski 3
II. The Different Types of Energy
Potential
Potential energy is energy of the position of an object in a system of mechanical
energy. It can also be thought of as stored energy. There is potential energy when anything is
suspended off the ground due to the force of gravity acting on the object. If the force holding the
object up in the air were to stop, the potential energy in the object would turn into kinetic energy
until it hit the ground, at which point there would be no more potential energy. A spring also has
potential energy when it is compressed, which is tuned into kinetic energy when the spring is
released.
Kinetic
Kinetic energy is energy of motion. Anything that is in motion has kinetic
energy. The amount of kinetic energy an object has is equal to one-half of its mass times its
velocity squared (1/2mv²). Therefore, the more mass something has or the greater its velocity,
the more kinetic energy it will have.
Mechanical
Mechanical energy encompasses these two types of energy. Mechanical energy is
the energy which is possessed by an object due to its motion or its stored energy of position
(www.physicsclassroom.com). Mechanical energy is any type of energy associated with motion.
Therefore heat, sound, and light are not mechanical energy because they are not associated with
the motion of objects, but kinetic and potential energy are mechanical energy.
III. The Law of Conservation of Energy and Momentum
Aisbet Becker, Bolwerk, Hoff, Serio, Zaporski 4
The laws of conservation of energy and momentum state that neither energy nor momentum can
be created or destroyed. Because of the law of conservation of momentum, we know that when
two objects com in contact with each other, the sum of their energies will remain the same before
and after the collision. Similarly, we know that according to the law of conservation of energy,
energy is never lost—but merely changed into another form or put into another object. For
example, a twisted rubber band, when released, will unwind, converting its potential energy into
the kinetic energy that spins a toy airplane’s propeller. Moving air and running water have
mechanical kinetic energy that can be transferred to windmills and turbines, which spin
generators that convert the mechanical energy to electrical energy. In all of these changes,
exactly the same amount of energy is present after the change as was present at the start.
(www.glenbrook.com)
Newton came up with the idea of the conservation of energy and momentum in order to
demonstrate and explain the fact that the amount of energy never changes. This useful principle
can be applied to all areas of life no matter where you are because you are constantly using
energy.
IV. Friction and Gravities Effects on Energy
Energy plays an important role in the motion of objects. However, energy is greatly
affected by both friction and gravity. Objects in motion are often slowed by friction when they
come in contact with another object. As Newton’s first law of motion states, any object in
motion will stay in motion unless some outside force is applied to it. Friction is the most
commonly seen of these forces. A famous example of this is a ball rolling on the ground. When
Aisbet Becker, Bolwerk, Hoff, Serio, Zaporski 5
force is applied to the ball, such as being kicked, the ball begins to move. Without friction, the
ball would infinitely keep rolling unless stopped by some other object. Friction, however, resists
the moving object and causes it to slow down until it stops. In other words, friction causes
objects to lose energy until there is no more kinetic energy to keep it moving.
Gravity also affects energy by constantly providing a pull towards earth. “The force of
gravity affects both light and all material bodies; since both carry energy, but only the bodies
carry mass, it follows that gravity will affect anything carrying energy” (Wudka). To again use
the example of a ball: If a ball is thrown into the air, it uses the kinetic energy of the person who
threw it. However, the pull of gravity provides a resistance that slows the ball down. Once the
ball reaches its peak, gravity then begins to increase its kinetic energy and pulls it quickly
towards earth. Sometimes the energy is released into the ground, and other times, the energy is
used by the ball, which then bounces upward again. Also, if a marble is placed on a downhill
track, it will travel more slowly than a marble dropped from a distance before hitting the track,
due to the energy that is built up by the pull of gravity. Gravity affects the motion of objects by
decreasing and increasing their kinetic energy, and in some cases, changing the direction of the
motion of an object. Friction and gravity both have excessive effects on energy in motion.
V .The Application of Energy
Both the pendulum and Newton’s Cradle use the conservation of momentum and the
conservation of energy. Conservation of momentum is the total momentum of a system of
objects stays the same. For example, when two objects collide, the momentum after the collision
equals that of the momentum before the collision. The velocities can change in magnitude and
direction, but the velocities of both objects are the same. There are two types of collisions. Either
a collision is elastic, and the objects are in contact with one another briefly, or inelastic (or
Aisbet Becker, Bolwerk, Hoff, Serio, Zaporski 6
perfectly inelastic) and the objects stay fixed together and move as one object having one
velocity.
Conservation of energy is the idea that energy only changes in form. It cannot be created
or destroyed. As an object loses energy from one form, it gains energy from another form. This
exchange takes place in kinetic and potential energy. Kinetic energy is energy connected with
motion. Potential energy is energy connected with position. A ball being thrown into the air is an
example of this. The ball loses velocity as it rises into the air, and consequently loses kinetic
energy. The ball gains gravitational potential energy as it soars higher in the sky. The ball
reaches its maximum height when all of the initial kinetic energy has been shifted to potential
energy.
The pendulum, originally at rest, collides with a projectile with the initial momentum.
The projectile stays fixed with the pendulum and moves as one with it, both having the same
final velocity and momentum. The pendulum then moves about a pivot, losing the kinetic energy
gained with the projectile and receiving potential energy until it reaches its maximum height. At
the point of the maximum height, all the kinetic energy has been transferred into potential
energy.
For Newton’s Cradle, when a ball is swung up and then let go, it hits the next ball in a
pendulum-like motion. The energy and momentum travel through each ball until reaching the
final ball. The last ball moves at the same speed as the first ball due to the force of collision
between the first ball and the following ball and so on. The number of balls pulled and let go
determines the number of balls that will move due to the collision. The moving balls will move
back and forth until they lose friction and slow down.
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Works Cited
www.glenbrook.com
“Lesson 17: Physics”. 18 December 2005.
<http://64.233.167.104/search?q=cache:6OPvznvqBocJ:www.itv.scetv.org/guides/Eye%
2520Wonder/17%2520Physics.pdf+and+gravity+affect+energy&hl+en.>
“Newton’s Three Laws of Motion”. Astronomy 161: The Solar System. 18 December 2005.
<http://csep10.phys.utk.edu/astr161/lect/history/newton3laws.html.>
physicsclassroom. 2004. The Physics Classroom and Mathsoft Engineering and
Education, Inc. 8 December 2005
<http://www.physicsclassroom.com/mmedia/energy/pe.html.>
School-for-champions. <http://www.scholl-for-champions.com/Science/newtons_cradle.html.>
Serway and Faughn. College Physics, vo. 1. New York: Brook/Cole Publishing Co, 2003.
U la.edu. <http:wla.edu/physics/labs/1401/1401Lab6.pdf.>
Wudka, Jose. Gravitation and Energy. 24 September 1998. University of California, Riverside:
Department of Physics.
<http://phyun5.ucr.edu/~wudka/Physics7/Notes_www/node91.html.>