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Velocity-Time Graphs:
Velocity versus time graphs represent changes that occur in an object's velocity with respect to time. The slope of the line is the acceleration (change in velocity divided by the change in time) of the object.
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The oil drop pattern uses dots to represent the location of the car after a certain interval of time - perhaps after every 1-second interval in time. An inspection of the location of each dot relative to the previous dots allows you to determine if the distance traveled in the most recent second is increasing, decreasing or staying the same. You can decide what type of motion is involved by observing how the distance traveled in each consecutive second is changing.
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It should be clear from the oil drop pattern that the object is moving with a changing velocity. The object changes its speed from a low velocity (slow) to a large velocity (fast). The velocity is negative the entire time. You must match this motion with the appropriate velocity-time plot.
Since the velocity is negative, you will need to pick a line that is in the negative region of the graph (above the time axis). Since there is an acceleration (that is, the velocity is changing), you will need to pick a line with a slope (see Know the Law section). Since the object is moving from slow to fast, you will need to pick a line that slopes downward from a nearly 0 velocity to a large negative velocity.
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