2 Kinematics - BC Science Physics 11

2.3 Uniform Acceleration
Warm Up
In your own words, describe the difference between average velocity, initial velocity, final velocity, and a change
in velocity.
Graphing
Acceleration
In a situation where the speed of a moving body increases or decreases at a uniform rate
the acceleration is considered uniform. This motion can be graphed on a speed vs. time
and will be linear (Figure 2.3.1). Since speed is the dependent variable, it is plotted on the
y-axis. Time, the independent variable, will be on the x-axis.
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54 Chapter 2 Kinematics © Edvantage Interactive 2012 ISBN 978-0-9864778-3-6
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Figure 2.3.1 This graph shows speed changing at a uniform rate.
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The y-intercept for the speed-time graph is b = v0 , where v0 is the speed of the
object at time t = 0. In Figure 2.3.1, the initial time is zero and the final time is t, so the
time interval is simply ∆t = t – 0 = t.
The slope of the graph is m = ∆v
= a, since acceleration is change in speed divided
∆t
by change in time.
If a = vf – v0 t
Then at = vf – v0 and
v f = v 0 + at
This is a general equation for any object that accelerates at a uniform rate. It says
that the final speed of the accelerating object equals the initial speed plus the change in
speed (at).
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