Motion - average velocity

8

Let us look at a motion which is not under constant velocity all of the time.

Start the animation and notice that the boat doesn't catch the wind equally all the time.

Determine the boats velocity in the time intervals:

0 s - 5 s (Answer)
0 s - 10 s (Answer)
0 s - 15 s (Answer)

In each of the three time intervals the motion is under constant velocity.

But as the velocity isn't a constant in the time interval 0 -15 s, we will define an average velocity in this time interval

With this velocity the sail would go off like this.

9

In this exercise You will be watching a match between to boats - a red one and a blue one - starting at the same time.

Start the animation, which runs for 15 seconds.

Determine the velocity of the red boat during the time period of 15 seconds. (Answer)

Determine the velocity of the blue boat during the time period of 15 seconds. (Answer)

During which of 3 time intervals do the boats share the same average velocity? (Answer)

10

A boat is going against the stream. At some moment the wind will fall letting the boat go with the stream.

Start the animation, which runs for 20 s.

During the time interval from t1 = 3 s to t2 = 7 s the boat covers a distance Ds = s2 - s1 = 25 m - 4,5 m = 20,5 m, which means that the average velocity vave of the boat has been

The average velocity vave in the time interval Dt expresses the slope of the secant, as shown on the graph.

In which time interval is the average velocity vave = 0 m/s? (Answer)

Determine the average velocity vave in the time interval from t1 = 15 s to t2 = 20 s. (Answer)

11

Now it's Your turn. Make the boat move according to the graph.

Initiate exercise 1.
In the graph widow You'll see the (
t,s)-graph, which the boat must follow during the 15 seconds the animation will run for.

Click on 'start' beneath when You are ready and then drag the boat along using the mouse.

Start exercise 1.

Start exercise 2.

Start exercise 3.

Start exercise 4.

Start exercise 5.

Move on to Motion - graphing velocity

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