Lab 11_Orbits - Lab 11: Newton's Laws, Planetary Orbits...

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Lab 11: Newton's Laws, Planetary Orbits Introduction Don't Panic - words inscribed in large friendly letters on the cover of the Hitchhikers Guide to the Galaxy by Douglas Adams . The introduction to this lab includes a number of equations and the exercise requires a calculator. Do not let the equations frighten you - they are the language of this part of the Universe. If you follow the instructions, the units will take care of themselves: work through the worked example on your own calculator to ensure that you are using your calculator correctly . Newton's Laws Up to the mid-seventeenth century, Planetary motions were predicted through equations that were based solely upon observations (Kepler's laws), with no theoretical basis for the equations. Isaac Newton made three assumptions , now called Newton's Laws of Motion, about the interactions among force, mass and motion, and showed that the equations used to describe planetary motions followed directly from these assumptions. Newton's First Law or the Law of Inertia . A body remains at rest, or moves In a straight line at constant speed, unless acted upon by an outside force. This law introduces the concept of acceleration, which is defined as a change of speed and/or a change in direction. Without an external force, a body will not accelerate. Acceleration is defined as the rate at which the speed of a body changes in a particular direction. As a car accelerates from a stop light, its speed changes in the forward direction. As a car turns a corner, it accelerates sideways! It moves in a direction perpendicular to its original motion, in addition to moving in its original direction, resulting in a curved path. Newton's Second Law . The acceleration of a body is proportional to the external force acting on the body and the mass of the body. This law is commonly expressed as an equation which states that if a force F acts on a body of mass m , it will accelerate In the direction of the force at rate a given by: Equation 1.
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The mass of a body is a measure of the total amount of material in the body, and is usually measured in grams or kilograms. Mass should not be confused with weight, which is a force caused by the Earth's gravity, and is given by the product of the mass and the acceleration caused by Earth's gravity (about 9.8 meters per second per second, or 9.8 m/s 2 ). Newton's Third Law . Whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body. This is the famous statement of action and reaction: every force has an equal and opposite reaction. As your weight pushes down upon the floor, the floor pushes back with an equal but opposite force, canceling the force of your weight. In addition to the three laws of motion, Newton also formulated a general statement
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This note was uploaded on 01/01/2011 for the course GLG 190 taught by Professor C.v. during the Spring '09 term at University of Arizona- Tucson.

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Lab 11_Orbits - Lab 11: Newton's Laws, Planetary Orbits...

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