Motion

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 I n physics, motion is changing place or form depending on time. Change in motion is the result of a force acted upon it. Motion is usually described in terms of velocity also seen as speed, acceleration, displacement, and time. An object's velocity cannot change unless it is acted upon by a force, as described by Newton's first law. Another name for this is called Inertia. An object's momentum is related to the object's mass and velocity, and the total momentum of all objects in a closed system does not change with time, as is mentioned in the law of conservation of momemtum.

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"Motion is defined as a change in position over time. The change can be in a horizontal direction, a vertical direction or in both directions. In order to detect motion, you need to have a reference point, in other words, something that is not moving or is moving at a different speed in order to help relatively mark your movement."(Robertson) So what exactly is a reference point? A place or object used for comparrison to determine if something is in motion. The reference point never moves no matter what. "Objects that are stationary make good reference points. Examples are a tree, a sign, and a building."(Jones 6-15) These make good reference points because objects around them are continuously moving and these objects are at a standstill. "An object is in motion if it changes poisition relative to its reference point."(Jones 6-15)" Reference points allow someone on a bike or skateboard to determine if additional force is needed or if less force is needed. A rider utilizes a point of reference in order to adjust their center of gravity, speed, momentum or other physical factors in determining the speed or motion needed for a given maneuver or series of tricks."(Robertson) Above are good reference points!  Measuring distance is done in the type of measurment is called the SI; which stands for International System of units. The SI unit of length is the meter(m). "The length of an object smaller than the meter is called the centimeter(cm)."(Jones 6-15) Velocity is speed in any givin direction. In Physics, velocity is the rate of change of posion. A mistake in finding velocity can trun into a collison or a problem. To explain and describe on objects motion, you need to know the direction. Knowing the velociy; is knowing the speed and direction of an object's motion."An object that is moving will continue moving at the same velocity forever, an object that is at rest will stay at rest." (Hakim 79, 82, 86-87) Velocity=acceleration. media type="custom" key="6185871" "The rate of change of velocity is acceleration– how an object's speed or direction changes over time, and how it is changing at a particular point in time.The rate of change of velocity is acceleration – how an object's speed or direction changes over time, and how it is changing at a particular point in time." (Resnick)

"The speed of an object is the distance the object travels per unit of time. To calculate the speed you need to know the distance an object travels."(Jones 6-15) The speed equation is distance/time. "To calculate the average speed you divide the total distance traveled by the total time."(Jones 6-15) You also have to calculate slope. The slope equation is rise/run. "The rise is the vertical distance from any two point on a line and the run is the horizontal difference between the same two points. Slope tells you the steepness of a line on a graph."(Jones 6-15) The last part of motion is graphing it. You can show the motion of an object on a line in which you plot the distacne verse time. Most ojects do not travel at a constant speed if they are moving. The pictures above are examples of slopes!



This is a picture of Galileo Galilei

Motion had to be invented by someone, and that someone is Galileo Galilei. He was born in Pisa, Italy in 1564. He studied the ideas of Archimedes; particularly the use of mathematics to solve physical problems. The study of Archimedes prinicples led him to conclude that all objects would fall at the same speed. Galileo unfortunitely died under house arrest in 1642. The painting "Falling Slowly" shows him demenstrating ideas by rolling balls down a slope. He reasoned that they would behave in the same way as falling objects, only more slowly. "The Aristolelians said that horizontal motion is straight. The law of free fall says that the vertical motion towards earth is the one that gets faster and faster."(Tesar, and Bunch 401-402) Galileo figures out that all trajectories which are a path of a moving through space, are combitionations of steady horizontal motion with changing vertical speed. He shows this result in parabalas.His research shows him that trajectories have two independent motions. On of the exampls is horizontal which carries a constant velocity. The other motion is vertical, which changes according to Galileo's free fall. Combining both paths produces a perdictable parabala curve!

This is a picture of Albert Einstein.

"In 1905 German scientist; Albert Einstein published a revolutionary new theory. It was called the Special Theory of Relativity. It dealt with effects on high-speed motion. Afetr much thought Einstien showed that for the speed of light to always be the same, distacnes much shrink and time must slow down at near light speeds." (Lafferty 24,30,58)

  "Sir Isaac Newton first presented his three laws of motion in the "Principia Mathematica Philosophiae Naturalis" in 1686. His first law states that every object remains at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia." (Benson)The main idea is that if there is no net force acting on an object then the object maintains a constant velocity. If that velocity is zero, then the object stays at rest. If the velocity is not zero, then the object maintains that velocity and travels in a straight line. If a net external force is applied, the velocity changes because of the force. The liftoff of a rocket from the launch pad is a good example of this principle. "The velocity of the rocket is zero and the rocket is at rest. If the rocket is sitting on its fins, the weight of the rocket is balanced by the re-action of the earth to the weight as described by Newton's third law of motion. There is no net force on the object, and the rocket would remain at rest indefinitely.When the engine is ignited, the thrust of the engine creates an additional force opposed to the weight. As long as the thrust is less than the weight, the combination of the thrust and the re-action force through the fins balance the weight and there is no net external force. The rocket stays on the pad. When the thrust is equal to the weight, there is no longer any re-action force through the fins, but the net force on the rocket is still zero. When the thrust is greater than the weight, there is a net external force equal to the thrust minus the weight, and the rocket begins to rise. The velocity of the rocket increases from zero to some positive value under the acceleration produced by the net external force." (Benson)

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Jones, T.Griffith.//Motion, Forces, and Energy.// Boston:Pearson, 2009. 6-15. Print.

Robertson, Bill. "Finding a Point of Reference-Motion." //EP Robertson Icorporated// (2007): n. pag. Web. 13 May 2010. [].

Resnick, Robert. "Velocity." //Wikipedia//. 7. Wikimedia Foundation, Inc, 2004. Web. .

Benson, Tom. "Newtons First Law." //National Aeronnautics and Space Administration//. NASA, Mar 16 2010. Web. 18 May 2010. [|http://www.google.com/imgres?imgurl=http://www.grc.nasa.gov/WWW/K-12/rocket/Images/newton1r.gif&imgrefurl=http://www.grc.nasa.gov/WWW/K-12/rocket/newton1r.html&usg=_8JmeW_2V99OQMJvh5APo3KvqTL4=&h=532&w=707&sz=23&hl=en&start=13&um=1&itbs=1&tbnid=gwLaupk3cDKxvM:&tbnh=105&tbnw=140&prev=/images%3Fq%3Dnewton%2527s%2Bfirst%2Blaw%2Bof%2Bmotion%26um%3D1%26hl%3Den%26sa%3DX%26tbs%3Disch:1,isz:m]

Lafferty, Peter. //Force & Motion//. London: Dorling Kindersely Eyewitness Books, 1992. 24,30,58. Print.

Tesar, Jenny, and Bryan Bunch. "Motion." //Science & Invention//. 3. Woodbridge, Conneticut: Blackbirch Press Inc., 2001. Print

Hakim, Joy. //The Story of Science Newton at the Center//. Washington: Smithsonian Books, 2005. 79, 82, 86-87. Print.