Graphing Motion Lesson 5

In our last lesson we learned about distance and time. We learned that distance and time were determined by speed and direction.

We discussed if two families are planning a car trip to the same place they would not travel the same distance in the same time unless they traveled the same direction and same speed as each other. Family 1Family 2

If Family 1 travels 60 miles per hour and Family 2 travels 40 miles per hour and they both travel in the same direction, Family 1 will arrive first to their destination. They are driving at a faster speed.

Family 1 traveled the same distance as Family 2 but they made better time than Family 2. They both followed the same direction, only Family 1 traveled at a greater speed than Family 2. Family 1 Family 2

Describing the motion of an object can be hard to do with words. Graphs can help make motion easier to picture.

Let’s review some of our vocabulary. Look back in your science notebook.

What is motion?

What is speed?

Speed is the rate at which an object covers a distance.

What is velocity?

Velocity tells the speed and direction of a moving object.

Plotting distance against time can tell you a lot about motion. When we plot distance and time we plot them on an axis.

What is an axis ?

Axis is a reference line drawn on a graph (you can measure from it to find values). Here is a graph with an X Axis and a Y Axis.

A graph can be created using one axis to show the distance that an object travels, and the other axis to show the period of time the object is traveling.

Time is always plotted on the X-axis (bottom of the graph). x y

On the next slide look at the numbers on the bottom line (time) the numbers increase moving to the right.

Distance is plotted on the Y-axis (side of the graph). x y

You can see that the distance begins with zero and increases as it moves up.

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 ”.

What information can we gather by looking at this graph showing distance and time?

We can see that distance and time are increasing at the same rate. This is called constant speed.

Constant speed is shown by straight lines on a graph.

Let’s look at these two moving objects. How are they different? How are they the same?

Both of the lines in the graph show that each object moved the same distance, but the steeper dashed line got there before the other one.

A steeper line indicates one group moved at a higher speed.

Both lines are straight, so both speeds are moving at a constant speed.

Graphs that show an increase or a decrease of speed 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.

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.

It is easy to create a graph to help you see the relationship between distance and time.

Let’s look back at our two families, Family 1 and Family 2. Family 1 traveled at a rate of 60 miles per hour. Let’s say they traveled 120 miles. It took them 120 minutes or 2 hours. Family 1 Family 2

Let’s create a graph to show Family 1’s trip DISTANCEDISTANCE BYMILESBYMILES Time by minutes

Let’s create a graph to show Family 1’s trip DISTANCEDISTANCE BYMILESBYMILES Time by minutes

Let’s add Family 2’s trip DISTANCEDISTANCE BYMILESBYMILES Time by minutes

They both moved at a constant speed. Family 1 only went at a faster speed DISTANCEDISTANCE BYMILESBYMILES Time by minutes

Answer the attached questions on the worksheet entitled L#5 Graphing Motion.

In our next lesson we will predict motion.

Good Job Today! And remember to….

See you next time!