# Motion - graphs

5

In a coordinate system we can plot the motion of a body. This is saying we draw a graph that shows us the position s as function of time t.

Start the animation and notice that every second the associated value of position s is measured.

The measurements of time and position belonging together is then plotted as points in a (t,s)-graph.

Please press the 'Reset'-button and use the 'Step'-functions and the mouse to check up on the measured points.

By connecting these points, we find that the graph is a straight line.

Now, determine the velocity of the skier.  (Answer)

6

We defined the velocity as

This expression has an important connection to the (t,s)-graph for the motion as we shall see now.

Remake the graph from the animation above.

As the graph is a straight line it makes sense to determine the slope a of the line by using the delta method.

Comparing the two expressions

we find that the slope of the line is equal to the skiers velocity.

7

You can determine the velocity of a body by looking only at the (t,s)-graph.

Show the graph of a body in motion and determine the velocity. (Answer)

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