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Home Minds On 1D Kinematics Mission KC8 Pos'n-Time and Vel-Time Data Help Help 5

Mission KC8 Pos'n-Time and Vel-Time Data

The Question

The velocity-time data sets below represent the motion of four objects. Which data set(s) depict(s) a negative acceleration? List all that apply ... .

Physics Rules

Direction of Acceleration:
Acceleration is a vector quantity and it has a direction. For an object moving in a straight line, the direction of the acceleration is dependent upon two factors:
 
  • the direction that the object moves, and
  • whether the object is speeding up or slowing down
 
If an object is speeding up, then the direction of the acceleration is in the same direction that the object is moving. If an object is slowing down, then the direction of its acceleration is in the opposite direction that the object is moving.

Think About It

One way for an object to have a negative acceleration is to move in the positive direction and slow down. Such an object has a positive velocity and a negative acceleration. (Incidentally, the other way to have a negative acceleration is to move in the negative direction and speed up.) In this question, each object has a positive velocity. So in this case the object(s) with negative acceleration is (are) slowing down; their magnitude of velocity is decreasing.

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