Major Ideas:
Speed
The motion of an object can be described by its speed and direction of travel. Every object has speed, whether it is moving or at rest. If the object is at rest, the speed is zero (m/s). To find out the exact speed, you would calculate: Speed= Distance / Time. Example: if the blue buggy traveled 6 meters in 3 seconds, then its speed would be 2 meters per second (m/s). Be sure to always include your units of measurement! If your distance was in meters and your time is in seconds, then your units would be m/s (meters per second). If your distance was in miles and your time was in hours, then your units would be mi/h or mph (miles per hour). Cars have speedometers that track the speed of the vehicle in miles per hour. We talk about speed in two ways, as constant or non constant. Constant Speed means the object's speed is not changing. Non Constant Speed means the object's speed is changing, either speeding up or slowing down. (We avoid saying acceleration and deceleration at the 6th grade level.)
Representing Constant and NonConstant Speeds
We will represent the motion of objects three ways in this unit: dot trails, bar graphs, and line graphs.
Dot Trails:
If there was a device, such as a dot car, that could mark a dot once every second, we would see a trail of dots representing the motion of the object. Depending on the object's speed, the distance between the dots would vary. For instance, if a buggy was going at a slow and constant speed, we would see evenly spaced out dots close together. If the buggy was going at a fast and constant speed, we would see evenly spaced out dots
farther apart. If a buggy starts off slow and gets faster, this nonconstant speed would be represented by dots that start out close together and get farther apart. If the buggy started off fast and slows down, this non constant speed would be represented by dots that start out far apart and get closer together.
Bar Graphs:
To represent speed on a bar graph, we would put interval distance on the yaxis and time on the xaxis. Therefore, for every time interval (usually every 1 second), it shows the distance the object traveled (for just that second alone). Since the dots on the paper mark our time interval (every second), we are able to measure the distance traveled each time to graph it. If all our bars are the same height, that means the buggy traveled at a constant speed (the same distance each time). If our bars slant upwards, that means the buggy traveled at a non constant speed and was getting faster (the time interval does not change so larger distances means the object speeds up think baby steps versus lunges). If our bars slant downwards, that means the buggy traveled at a non constant speed and was getting slower.
Line Graphs:
Line graphs compile all of the bars of our bar graph. In other words, the line graph takes into account the total distance traveled by the object. The total distance goes on the yaxis and the time interval stays on the xaxis. For instance, if a bar graph shows a buggy going at a constant speed of 2 meters per second, then its bars are the same height (all at 2 meters). On the line graph, the graph would show a straight incline, its slope* going up
by 2 each time because at 1 second the buggy went 2 meters, at 2 seconds the buggy had traveled 4 meters, at 3 seconds the buggy had traveled a total of 6 meters and so on. The line is angled upwards because the buggy was traveling away from its original location. If a buggy was going at a constant speed (always the same distance each time), but it was traveling towards the "start" line, then the graph would show a straight, or linear, line but facing downwards. When an object is going a non constant speed, its bars are different heights. Therefore, the slope* of our line on the line graph would also change. The differences in slope cause our line graph to show a curved, or non linear line. If an object starts out slow and speeds up, the rise each interval would be small and get larger over time, causing a curve upwards. If the object starts out fast and slows down, the rise of each interval would be large and get smaller over time, causing the curve to "taper" off or
almost flatten out. On a line graph, a flat line (completely horizontal) shows the object is not gaining any
distance over several intervals, which means it is at rest (not moving).
*Slope is a term used in math to describe the steepness of a line. It is determined by the change up and down (rise or yaxis) over the change side to side (run or xaxis) on a line graph. For information, click here.
Dot Trails:
If there was a device, such as a dot car, that could mark a dot once every second, we would see a trail of dots representing the motion of the object. Depending on the object's speed, the distance between the dots would vary. For instance, if a buggy was going at a slow and constant speed, we would see evenly spaced out dots close together. If the buggy was going at a fast and constant speed, we would see evenly spaced out dots
farther apart. If a buggy starts off slow and gets faster, this nonconstant speed would be represented by dots that start out close together and get farther apart. If the buggy started off fast and slows down, this non constant speed would be represented by dots that start out far apart and get closer together.
Bar Graphs:
To represent speed on a bar graph, we would put interval distance on the yaxis and time on the xaxis. Therefore, for every time interval (usually every 1 second), it shows the distance the object traveled (for just that second alone). Since the dots on the paper mark our time interval (every second), we are able to measure the distance traveled each time to graph it. If all our bars are the same height, that means the buggy traveled at a constant speed (the same distance each time). If our bars slant upwards, that means the buggy traveled at a non constant speed and was getting faster (the time interval does not change so larger distances means the object speeds up think baby steps versus lunges). If our bars slant downwards, that means the buggy traveled at a non constant speed and was getting slower.
Line Graphs:
Line graphs compile all of the bars of our bar graph. In other words, the line graph takes into account the total distance traveled by the object. The total distance goes on the yaxis and the time interval stays on the xaxis. For instance, if a bar graph shows a buggy going at a constant speed of 2 meters per second, then its bars are the same height (all at 2 meters). On the line graph, the graph would show a straight incline, its slope* going up
by 2 each time because at 1 second the buggy went 2 meters, at 2 seconds the buggy had traveled 4 meters, at 3 seconds the buggy had traveled a total of 6 meters and so on. The line is angled upwards because the buggy was traveling away from its original location. If a buggy was going at a constant speed (always the same distance each time), but it was traveling towards the "start" line, then the graph would show a straight, or linear, line but facing downwards. When an object is going a non constant speed, its bars are different heights. Therefore, the slope* of our line on the line graph would also change. The differences in slope cause our line graph to show a curved, or non linear line. If an object starts out slow and speeds up, the rise each interval would be small and get larger over time, causing a curve upwards. If the object starts out fast and slows down, the rise of each interval would be large and get smaller over time, causing the curve to "taper" off or
almost flatten out. On a line graph, a flat line (completely horizontal) shows the object is not gaining any
distance over several intervals, which means it is at rest (not moving).
*Slope is a term used in math to describe the steepness of a line. It is determined by the change up and down (rise or yaxis) over the change side to side (run or xaxis) on a line graph. For information, click here.
Video: Graphing Changes in Motion
>> Video: Finding Speed on a D v.T Line Graph >> Video: Interpreting motion on bar and line graphs >> 

Forces
A force is a push or pull on an object. In this unit, we discuss several forces and how they can affect the motion of an object. By the end, students must be able to idenify these forces within a picture, sentence, or diagram. To identify them, students must first know what each one is. See their definitions below:
Gravity a force that pulls vertically downward* on all objects, all of the time
Friction a rubbing motion that prevents objects from moving or creates motion
Tension Force a rope, string, strap, or cable pulling on an object
Support Force a force that keeps objects from falling, usually under or beneath the
object pushing up against gravity
Elastic Force a push or pulling force that stretches and goes back, very bouncy
Air Resistance acts opposite of an object moving through the air
Human Force a push or pull by a human
*Vertically downwards means towards the center of the Earth.
Forces can be balanced or unbalanced. Balanced forces mean all forces are acting equally and the object's motion will remain at a constant speed (either moving or at rest). Unbalanced forces mean one force is greater (bigger) than the other and the motion of the object will change (nonconstant speed, either speeding up or slowing down). The object will move in the direction of the larger force when they are unbalanced.
Mass vs. Weight
There is a difference between "weight" and "mass". Mass is how much stuff we are made of, while
weight measures how hard Gravity is pulling down on you. Think about it! When you "weigh" yourself, the scale is between you and the floor. Gravity pulls vertically downward at a rate of 9.8 meters per second squared on Earth. The moon has less gravitational pull so if you were to weigh yourself on the moon, your scale would read much less (about 1/3 less)! Mass, however, stays the same everywhere (you are still the same amount of person on both the Earth and the Moon).
Gravity a force that pulls vertically downward* on all objects, all of the time
Friction a rubbing motion that prevents objects from moving or creates motion
Tension Force a rope, string, strap, or cable pulling on an object
Support Force a force that keeps objects from falling, usually under or beneath the
object pushing up against gravity
Elastic Force a push or pulling force that stretches and goes back, very bouncy
Air Resistance acts opposite of an object moving through the air
Human Force a push or pull by a human
*Vertically downwards means towards the center of the Earth.
Forces can be balanced or unbalanced. Balanced forces mean all forces are acting equally and the object's motion will remain at a constant speed (either moving or at rest). Unbalanced forces mean one force is greater (bigger) than the other and the motion of the object will change (nonconstant speed, either speeding up or slowing down). The object will move in the direction of the larger force when they are unbalanced.
Mass vs. Weight
There is a difference between "weight" and "mass". Mass is how much stuff we are made of, while
weight measures how hard Gravity is pulling down on you. Think about it! When you "weigh" yourself, the scale is between you and the floor. Gravity pulls vertically downward at a rate of 9.8 meters per second squared on Earth. The moon has less gravitational pull so if you were to weigh yourself on the moon, your scale would read much less (about 1/3 less)! Mass, however, stays the same everywhere (you are still the same amount of person on both the Earth and the Moon).
GForce One Plane simulates zerogravity!
Representing Forces with Force Diagrams
A force diagram is a picture that shows all forces acting on an object. The forces are labeled and represented by arrows on the diagram; The larger the force, the longer the arrow that should be drawn. The direction of the arrow head indicates the direction that the force is acting. Remember, Gravity is always vertically downward!
To make sure you have a complete force diagram, follow SID:
Sketch the object,
Identify all forces,
Draw the arrows using the correct length and direction.
Students will be required to create force diagrams without looking at their notes. It is generally a difficult task so practice, practice, practice at home!
To make sure you have a complete force diagram, follow SID:
Sketch the object,
Identify all forces,
Draw the arrows using the correct length and direction.
Students will be required to create force diagrams without looking at their notes. It is generally a difficult task so practice, practice, practice at home!
Total Force
Total force is the combination of all forces acting on an object. When two or more forces are acting on an object, the object will ultimately go in the direction of the largest force. The size of the other forces, however, can alter the direction slightly or affect how far it will go.
The size of forces are measured in Newtons (N), named after Sir Isaac Newton who studied them.
When forces are acting in opposite directions from one another, we call them opposing forces. Opposing forces work against one another and have a minimizing effect. For instance, if an object is being pulled by to the left by a force of 10N and to the right by a force of 4N, the object will ultimately move 6N to the left. When forces are going in the same direction, we call them supporting forces. Supporting forces should not be confused with the Supportive type of force such as a table or chair! Supporting forces help one another and have a additive effect (add together). For instance, if that same object was being pulled to the left by a force of 10 N and also pushed to the left by a force of 4 N, the object will ultimately move 14N to the left. When sketching diagrams to
represent total forces, the length of the arrow should match the size of the force (larger forces have longer arrows).
Total force is the combination of all forces acting on an object. When two or more forces are acting on an object, the object will ultimately go in the direction of the largest force. The size of the other forces, however, can alter the direction slightly or affect how far it will go.
The size of forces are measured in Newtons (N), named after Sir Isaac Newton who studied them.
When forces are acting in opposite directions from one another, we call them opposing forces. Opposing forces work against one another and have a minimizing effect. For instance, if an object is being pulled by to the left by a force of 10N and to the right by a force of 4N, the object will ultimately move 6N to the left. When forces are going in the same direction, we call them supporting forces. Supporting forces should not be confused with the Supportive type of force such as a table or chair! Supporting forces help one another and have a additive effect (add together). For instance, if that same object was being pulled to the left by a force of 10 N and also pushed to the left by a force of 4 N, the object will ultimately move 14N to the left. When sketching diagrams to
represent total forces, the length of the arrow should match the size of the force (larger forces have longer arrows).
Video: Review of Balanced and Unbalanced Forces. Also, how to find the Total Force. >> Video: More on how to find the Total, or "net", Force. >> 
