query 03

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course Phy 201

003. `Query 3

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Question: What do the coordinates of two points on a graph of position vs. clock time tell you about the motion of the object? What can you reason out once you have these coordinates?

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Your solution:

They tell you the difference in distance travelled and time clock. That basically means how far it has gone in a given amount of time. When you have these coordinates, you can calculate the average rate of change/velocity.

confidence rating #$&*: 3

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Given Solution: The coordinates a point on the graph include a position and a clock time, which tells you where the object whose motion is represented by the graph is at a given instant. If you have two points on the graph, you know the position and clock time at two instants.

Given two points on a graph you can find the rise between the points and the run.

On a graph of position vs. clock time, the position is on the 'vertical' axis and the clock time on the 'horizontal' axis.

• The rise between two points represents the change in the 'vertical' coordinate, so in this case the rise represents the change in position.

• The run between two points represents the change in the 'horizontal' coordinate, so in this case the run represents the change in clock time.

The slope between two points of a graph is the 'rise' from one point to the other, divided by the 'run' between the same two points.

• The slope of a position vs. clock time graph therefore represents rise / run = (change in position) / (change in clock time).

• By the definition of average velocity as the average rate of change of position with respect to clock time, we see that average velocity is vAve = (change in position) / (change in clock time).

• Thus the slope of the position vs. clock time graph represents the average velocity for the interval between the two graph points.

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Self-critique (if necessary): OK

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Self-critique Rating: OK