All objects posses some form of energy. In this unit we will be exploring Kinetic Energy and Potential Energy. Kinetic Energy is the energy of motion. The faster an object moves the more kinetic energy the object has. Potential Energy is the energy of position. The higher the object is away from earth the greater the amount of potential energy is stored inside the object. A wind up toy is another example of these two types of energy. When I wind up a little toy car I am adding potential energy. Once I let the car go it begins to convert the potential energy into kinetic energy. The total amount of energy remains the same. Energy is always being converted from one form to another. Here are some examples of kinetic and potential energy:
Running Person Flying Bird |
A Car Parked Near the Top of a Hill A Monkey Hanging from a Tree |
Just think….when an object is sitting still it has the potential to move. When a roller coaster car is at the top of a hill the car is filled with potential energy. As the car moves down the hill it picks up speed. As the car picks up speed the kinetic energy increases. Once again kinetic and potential energy is being converted from one form to another. Lets see if this picture helps a little bit.
Time is measured in seconds, hours or minutes.
Speed is how fast an object moves. Rate of change of position.
Try these sample problems for a little practice. You can complete these questions for extra credit.
The axes have to be labeled with the name of the quantity being measured and the units.
The point where the two axes intersect is the origin. The origin usually has a value of (0,0).
* The x-axis is the time.
* The y-axis is the distance from the origin.
1.Count how much the Y value changes from on point to the other. This is the RISE.
2.Count how much the x value changes from on point to the other. This is the RUN.
On a speed graph, the slope is the same as the average speed between the two points.
Box 2: What is speed?
What exactly is speed? I am sure you have a rough idea. Speed is how fast something moves. But more exactly the speed of an object is the distance traveled over time. Speed is how far you travel in a certain amount of time. For example, when driving a car you would not exceed the speed limit of 55 miles per hour. Miles refers to the distance traveled and hour refers to the amount of time. If you were to travel a steady 55 miles per hour on the expressway for every hour you travel you would cover a distance of 55 miles. This brings us to the formula for speed. I am going to give you a little trick to help you with formulas. When you see the word "per" that is a signal to use division. If speed were measured as miles per hour, then we would assume that miles would be distance and hour would be time. So the formula for speed would be Distance divided by Time. Lets place the letters in the triangle below:
When you look at the formula for speed you may wonder why the “s” was left out. "V" was used to represent velocity. Velocity is speed with a direction (ex. 55 miles per hour due East).
The units used for speed will vary based on what you are measuring. For example: time can be measured in seconds, minutes or hours. Distance can be measured in meters or Kilometers (distance can be measured as a meter using any prefix such as Kilo-, centi-, mili- etc…). For speed we can combine the two units of measure: meters per second or kilometers per hour (Any combination will do, as long as it makes sense with the question.).
Box 3:Velocity/Speed Word Problems and Graphs
The units used in the word problems will provide clues to help you solve these tricky problems.
Distance is measured in meters.
*Practice Problems*
*Word Problems*
>Representing Data by using a Graph
Speed Graphs
Slope of a Graph
To find the slope of a line drawn between two points on a graph, use the following procedure:
Classnotes 10/17/01
Frame of Reference-
The motion of other objects is relative to your position and or motion.
Position of an object related to ones own.
Frame of Reference Demo
Frame of Reference in Relation to the Stars
Teminal Velocity: All object fall to Earth at the same rate: 9.8 meters per second squared. Some objects reach a point where they will stop accelerating. This point is called terminal velocity. For example if a bowling ball and a feather where dropped at the same time the bowling ball would land first due to the fact that the feather reached terminal velocity soon that the ball. The feather had some wind resistance that the ball did not.
This page is still under construction. Check back by 10/21/01
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