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course_planning:course_notes:relative_motion [2014/06/19 02:01] – created caballero | course_planning:course_notes:relative_motion [2014/06/19 02:33] (current) – caballero | ||
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===== Relative Motion ===== | ===== Relative Motion ===== | ||
+ | All motion requires a frame of reference, an origin from which to make measurements of displacement, | ||
+ | {{youtube> | ||
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+ | We need a way to describe measurements in frames that are moving relative to each other. Consider the example of the truck and the pitching machine in the video above. The truck moves to the left with a speed of 100km/hr while the baseball is fired from the truck to the right with a speed of 100km/hr. In the frame of the camera, which is on the ground, the baseball appears to have no horizontal velocity. ((When the baseball strikes the ground, it is spinning so it bounces off the ground and begins to move, but this not because it has any linear velocity in the fixed frame of the camera.)) | ||
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+ | ==== Computing relative velocities ==== | ||
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+ | In the diagram below, the truck appears at the instant the baseball leaves the pitching machine. | ||
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+ | {{ course_planning: | ||
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+ | There are three velocities that we are interested in: | ||
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+ | * $\vec{v}_{T/ | ||
+ | * $\vec{v}_{B/ | ||
+ | * $\vec{v}_{B/ | ||
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+ | They are related through vector addition: $\vec{v}_{B/ | ||
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+ | $$\vec{v}_{A/ |