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Newton's 1st Law of Motion - Translational Equilibrium
Commercial Airliner: The four major forces acting upon the airliner is lift, weight, thrust, and drag. If we consider the motion of the aircraft that is flying perfectly horizontal at a constant altitude, the lift that is created by the difference in air pressure is equal to the weight of the airplane, and the plane is not moving up or down. A cruising aircraft is flying through the air, and the thrust created by the engines is equal to the drag created by air resistance against the plane. Therefore, because the net force on the aircraft is zero, it travels with a constant velocity in one direction. If the pilot changes the power of the engines, the drag and the thrust are no longer in balance. The unbalanced forces cause the plane to undergo acceleration, and its velocity increases. However, the drag also increases with an increased velocity. In time, the drag catches up with the new thrust, the forces become balanced, and the acceleration ceases. The airplane will continue to fly at this new constant velocity until another variable changes. In this example, many other variables can throw the plane out of equilibrium. On a real aircraft, small changes in the throttle and flaps settings, decreases in weight due to fuel usage, and changes in wind speed can cause the plane to fall in and out of equilibrium over time. However, for demonstration purposes, these (small) variables are disregarded.
Picture of Newton: http://idology.wordpress.com/2008/12/24/what-are-we-feeding-the-metaphysics-of-branding/
Latin and English Definition: http://en.wikipedia.org/wiki/Newton's_laws_of_motion
Skydiving Cat: http://fiveprime.org/hivemind/User/Hoks
What I have found difficult concerning what I have studied is how to accurately draw the FBDs with the correct angles and labels while not forgetting or adding too many forces. After that, the next hardest thing is to write the equations and plug in the right variables, whether the x-component is the cos of theta and the y-component is the sin of theta, or vice versa. From there, it is just a simple task of solving the equations for any force.
My problem solving skills during this lesson are fairly stable. I try to put all of my effort into every problem, and if I am frustrated or stuck on a certain question, I know that all I need to do is to take a step back and look at it from another point of view until I understand the concept. The hardest thing for me is just to think about how to do the problem and do it quickly. For example, when we were working with inclined planes, it was sometimes hard for me to know how to find and where to write the angle theta in the FBD. However, I soon found out that I could find the angles using simple properties from Geometry and that it is usually easier if one writes them in relation to the x-axis. Nevertheless, I feel that my strengths are greater than my weaknesses. I feel that I am capable of understanding the problems and solving them in a correct manner. I organize my information and data to make it easy to see and try to draw my FBDs neatly and accurately.
During this lesson, I learned numerous things. This is what I learned about Newton's First Law of Motion and Translational Equilibrium:
As stated to the left in both the original Latin and English translation, Newton's First Law of Motion describes the common behavior of objects to "keep on doing what they're doing" unless they are acted upon by an outside unbalanced force. From this statement, one can conclude that the only way for an object to accelerate is for the sum of the forces upon an object to be unbalanced, or not equal to zero. If this is not true and the forces are balanced and cancel each other out, then the object is in translational equilibrium.
Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare.
Every body persists in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed.
An object is in translational equilibrium if and only if the vector sum of the forces on the object is zero, or SigmaFx = 0 and SigmaFy = 0. This knowledge, along with information from free-body-diagrams (FBDs) can be used to write equations that can be used to find all of the forces acting upon an object. such as normal, gravitational, tension, and other forces.
There are many excellent examples of Newton's First Law of Motion involving aerodynamics. The motion of an airplane when the pilot changes the throttle setting of the engine is described by the first law. The motion of a skydiver down through the atmosphere that has reached terminal velocity or that of a crazy kitty being launched up into the atmosphere are both examples of Newton's first law. Also, an asteroid that is floating through endless space shows how an object that is not affected by outside forces would continue at a constant velocity in the same direction forever.