lecture7

# lecture7 - So forces are synonymous with accelerations In...

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So, forces are synonymous with accelerations. In other words, a force is a push or a pull on an object that can overcome the object’s inertia and produce an acceleration. Now, for a given force, what determines how much acceleration I’m going to get? It’s the object’s INERTIA ! The more inertia (and thus mass) an object has, the more it resists a change its motion in its motion. = a m F v v Newton’s 2 nd Law This is Newton’s 2 nd Law. In words it says: The sum of the forces acting on an object is equal to its mass times its acceleration. Notice that forces are vectors . They require both magnitude and direction to completely describe them. Units? n ccelerati ass m g m kg ewton [ ][ ] on Accelerati Mass [ ] = 2 s kg = 2 s [ ] N = Newton It takes about 1 N of force to push a stamp on an envelope.

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Frames of reference: Newton’s First Law (and 2 nd Law) may be invalid depending on an observer’s frame of reference . Your frame of reference (or reference frame) is your perspective from which you observe a physical system. In physics we attach a set of coordinate axes to our frame of reference so that we can measure things like position, velocity, and acceleration. For example, let’s say you are standing at rest watching a passenger train go by you at constant speed. I’m sitting in my seat on the train with my lap tray down as I enjoy my favorite cold beverage. An ice cube from my drink is sitting on the tray in front of me. As the train goes by you, we both agree that the ice cube is obeying Newton’s gy y , g y g First Law: You see the ice cube continue to move in a straight line at constant speed.
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lecture7 - So forces are synonymous with accelerations In...

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