08_velocity - Lesson 8 Velocity Two branches in physics...

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Lesson 8: Velocity Two branches in physics examine the motion of objects: Kinematics : describes the motion of objects, without looking at the cause of the motion (kinematics is the first unit of Physics 20). Dynamics : relates the motion of objects to the forces which cause them (dynamics is the second unit of Physics 20). As we work through these two units on kinematics and dynamics (and through the rest of physics) we will discuss two kinds of measurements (quantities): scalar : scalars have magnitude (a number value), but no direction. Examples: time, mass, distance. Mass is a great example, since it has a number value (like 58 kg), but we don't give it a direction (like “East”). vector : have magnitude and direction Examples: velocity, force, displacement. Force has a magnitude (like 37 N) and a direction (like "pushed to the left"). Displacement & Time In kinematics we need to be able to have a way to describe the motion of the objects we will be studying, whether it's a car or an atom. The most basic information you must have to describe the motion of an object is its displacement , and the time it took to move that far. The displacement of an object is always measured from some reference point (which is usually “zero”, at a location at the start of the motion of the object). Although we use the words “ distance ” and “ displacement ” interchangeably in everyday language, they mean very different things in physics. The distance between two objects is scalar, since it doesn't matter which direction you measure it from. e.g. “We are standing 2.3m apart.” The displacement of an object is a vector, since you have to state the direction the object has traveled. e.g. “The car moved 2.56km east.” The most simple formula for calculating the displacement of an object is… Δd = d f - d i The Δ symbol is the greek letter “delta” and means “a change in…” The subscript “f” and “i” stand for final and initial. So, in this formula, we calculate the displacement of an object by taking the final position minus the initial position. 7/22/2011 © studyphysics.ca Page 1 of 6 / Section 1.1 Quantity ” is the root word for "quantitative" measurements. This means you're supposed to get a number answer. A “qualitative” measurement describes qualities of the data, like “the apple is red.”
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Example 1: A truck is passing a mark on the road that says 300m, and then passes another one 10s later that says 450m. Determine the distance the truck moved.
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