Thanksgiving Break Challenge!!

We have been learning about motion graphs and we know that describing the motion of an object is occasionally hard to do with words. So we use graphs help make motion easier to picture, and therefore understand.

Remember:
• Motion is a change in position measured by distance and time.
• Speed tells us the rate at which an object moves.
• Velocity tells the speed and direction of a moving object.
• Acceleration tells us the rate speed or direction changes.

Let's review DISTANCE-TIME GRAPHS:

Plotting distance against time can tell you a lot about motion. Let's look at the axes:
 
Time is always plotted on the X-axis
(bottom of the graph). The further to
the right on the axis, the longer the
time from the start.

Distance is plotted on the Y-axis (side
of the graph). The higher up the
graph, the further from the start.






If an object is not moving, a horizontal line is shown on a distance-time graph:


Time is increasing to the right, but its
distance does not change. It is not
moving. We say it is At Rest.










If an object is moving at a constant speed, it means it has the same increase in
distance in a given time:

Time is increasing to the right, and distance
is increasing constantly with time. The
object moves at a constant speed.

Constant speed is shown by straight lines on a graph.









Graphs that show acceleration look different from those that show constant speed.

The line on this graph is curving upwards. This
shows an increase in speed, since the line is
getting steeper:

In other words, in a given time, the distance the
object moves is change (getting larger). It is
accelerating.


























Summary:
A distance-time graph tells us how far an object has moved with time.
• The steeper the graph, the faster the motion.
• A horizontal line means the object is not changing its position - it is not moving,
it is at rest.
• A downward sloping line means the object is returning to the start.

Challenge Questions

 Please answer the questions to the following challenge on a blank sheet of paper and give to me when you return on Monday, December 2, 2013:

Look at the graph above. It shows how three runners ran a 100-meter race.

1. Which runner won the race? Explain your answer.

2. Which runner stopped for a rest? Explain your answer.

3. How long was the stop? Explain your answer.

4. How long did Bob take to complete the race? Explain your answer.

5. Calculate Albert’s average speed. (Figure the distance and the time first!)