LAB #5
VELOCITIES
Introduction:
When we talk about motion, we are describing a physical body changing
its position in time with respect to some frame of reference: usually the one in which the
observer is at rest. The motion of the body may be complicated, and you will have a
chance to analyze many such motions in your Physics course. However, we will start
with the simple case of a body moving in a straight line.
In Physics, motion in one dimension is described in mathematical terms by giving the
position of the body as a function of time. The average velocity during a certain time
interval is defined as the “distance traveled” in the time interval divided by the “time
interval”.
Instantaneous velocity is a more abstract concept than average velocity. It refers to the
velocity at one particular time, not the average over some time interval. Since in practical
terms we always need a finite time interval and distance covered for a velocity
measurement, we can only approximate instantaneous velocity measurement by making
our intervals as small as possible.
Average velocity is defined as distance traveled in an interval of time divided by the
elapsed time. This agrees with our everyday notion of the word speed. Velocity is defined
as a vector, for which the direction as well as the speed is important. In this experiment
all the motion is in a single straight line, so here there is no real difference between
"velocity" and "speed" except a + or  sign.
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 Fall '08
 RABE
 Physics, Space, Velocity

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